Grolier Multimedia Encyclopedia 1997

home *** CD-ROM | disk | FTP | other *** search

/ Grolier Multimedia Encyclopedia 1997 / GME97.iso / att / win31 / disk3 / answers.ht_ / answers.bin

Wrap

Text File | 1996-05-28 | 53KB | 1,179 lines

<TITLE>Netscape Handbook: Answers to Tough Questions</TITLE> <A NAME="C0"> Answers to tough questions </A> <ol> <A HREF="../index.htm">Netscape Handbook: Table of Contents</A> <li><a href="answers.htm#C1">Can you summarize the Options/Preferences menu items?</a> <li><a href="answers.htm#C2">What does each part of an Internet address mean?</a> <li><a href="answers.htm#C3">How do I install and configure helper applications?</a> <li><a href="answers.htm#C4">What are the MIME types used by helper applications?</a> <li><a href="answers.htm#C5">Can you summarize the Usenet newsgroup screens?</a> <li><a href="answers.htm#C6">Why might I use Gopher?</a> <li><a href="answers.htm#C7">Why might I use FTP (file transfer protocol)?</a> <li><a href="answers.htm#C8">What is a cache and how does it work?</a> <li><a href="answers.htm#C9">What is the difference between memory cache and disk cache?</a> <li><a href="answers.htm#C10">What is the recommended size for each cache?</a> <li><a href="answers.htm#C12">Where can I learn about Internet security?</a> <li><a href="answers.htm#C13">Can I safely transmit personal information such as credit card numbers?</a> <li><a href="answers.htm#C14">How does Netscape's security technology protect me?</a> <li><a href="answers.htm#C15">To what degree can SSL security protect me?</a> <li><a href="answers.htm#C16">How can I tell when security is in effect?</a> <li><a href="answers.htm#C17">What does the Document Information dialog box tell me?</a> <li><a href="answers.htm#C18">Are certificates required and where do you get one?</a> <li><a href="answers.htm#C19">Can one certificate be used on multiple servers?</a> <li><a href="answers.htm#C20">Do security features impose limitations on the ability to access sites?</a> <li><a href="answers.htm#C21">How can I save files and images onto my hard disk?</a> <li><a href="answers.htm#C22">What is dithering and how is it used?</a> <li><a href="answers.htm#C23">How do you create hierarchical menus?</a> <li><a href="answers.htm#C24">How do you convert hotlists to bookmarks?</a> <li><a href="answers.htm#C27">Are there any Windows-specific tips or tricks?</a> <li><a href="answers.htm#C38">What are Windows 95 Internet shortcuts?</a> <li><a href="answers.htm#C29">What is the World Wide Web's place in the Internet?</a> <li><a href="answers.htm#C30">How can I access the Internet?</a> <li><a href="answers.htm#C31">What are SLIP and PPP?</a> <li><a href="answers.htm#C32">What are TCP/IP and Winsocks?</a> <li><a href="answers.htm#C33">What should I know about firewalls?</a> <li><a href="answers.htm#C34">What are proxies and SOCKS?</a> <li><a href="answers.htm#C35">How do server push and client pull work?</a> <li><a href="answers.htm#C36">What are MIME, Types files, and Mailcap files?</a> <li><a href="answers.htm#C37">How do I learn to write HTML and publish pages?</a> </ol> <HR ALIGN="right"WIDTH=85%> <A NAME="C1"> Can you summarize the Options/Preferences menu items? </A> <DT>Window Styles <DD>Designate a home page and specify the style of toolbar buttons. <DT>Link Styles <DD>Choose to underline links and specify the longevity of followed links. <DT>Fonts <DD>Select proportional and fixed fonts for a particular encoding. <DT>Colors <DD>Select link colors and background pattern. <DT>Mail <DD>Specify a mail server, user name, e-mail address, and signature file for sending mail (and to establish a viable incoming mail address so others can respond). <DT>News <DD>Specify the host name for the news server (that supplies Usenet newsgroups), a News RC directory, and display criteria. <DT>Cache <DD>Specify the size and location of your disk cache and/or memory cache. <DT>Network <DD>Specify the size of a network buffer and the maximum number of network connections. <DT>Images <DD>Determine a priority for loading images and, depending on the platform, the manner that colors are approximated. <DT>Security <DD>Specify whether you receive notification dialog boxes regarding the state of a document's security. <DT>Directories <DD>Designate the temporary directory (before a helper application launches a file, Netscape saves the file to disk in the temporary directory). <DT>Applications <DD>Specify the location of these supporting applications: Telnet, HTML Source Viewer, and TN3270. Proxies <DD>Designate proxies and ports for FTP, HTTP, Gopher, News, WAIS Security, and SOCKS host protocols. <DT>Helper Applications <DD>Map MIME types and extensions of external applications and, depending on the platform, actions to take. <HR ALIGN="right"WIDTH=85%> <A NAME="C2"> What does each part of an Internet address mean? </A> The first part, yourName, identifies a user. The @ symbol (pronounced "at") separates the user name from the location of the server computer. The last part, aserver.bserver.org, identifies the location of the server computer. Addresses use lowercase letters without any spaces. The name of a location contains at least a string and, typically, a three-letter suffix, set apart by a dot (the period symbol is pronounced "dot"). The name of a location might require several subparts to identify the server (a host name and zero or more subdomains), each separated by dots . The three-letter suffix in the location name helps identify the kind of organization operating the server. (Some locations use a two-letter geographical suffix.) Here are the common suffixes and organizational affiliation: <ul> <li>.com (commercial) <li>.edu (educational) <li>.gov (government) <li>.mil (military) <li>.net (networking) <li>.org (noncommercial) </ul> E-mail addresses from outside the United States often use a two-letter suffix designating a country. Examples are: <ul> <li>.jp (Japan) <li>.uk (United Kingdom) <li>.nl (The Netherlands) <li>.ca (Canada) </ul> <HR ALIGN="right"WIDTH=85%> <A NAME="C3"> How do I install and configure helper applications? </A> To install and configure helper applications (many are already configured), use the Helper Applications panel. Helper applications expand Netscape's abilities. Netscape uses these applications to let you automatically decompress downloaded applications, listen to sounds, play movies, and get better display of images. Most can be obtained free or as shareware. Compression: You may find that programs are stored on the Internet in formats that your computer doesn't understand. You may need to locate a helper application program like PKUNZIP (Windows) to translate and decompress downloaded software (and other helper applications). Sounds: Most sound files aren't in a format that your computer can automatically play. To listen to the different types of sound files such as ULAW (common .au files), AIFF, and WAV, you'll need to install a helper application that understands them. Pictures and Movies: Netscape can display GIF, JPEG, and XBM files internally, but you may prefer to use a dedicated image viewer. To have Netscape automatically launch an external viewer, select the Mime Type in the list, then choose the radio button Launch Application. You'll need a player to view mpeg movies. <HR ALIGN="right"WIDTH=85%> <A NAME="C4"> What are the MIME types used by helper applications? </A> HTTP (HyperText Transfer Protocol) servers use HTML formatting. Netscape software has the built-in capability to read HTML-formatted pages (as well as the GIF, JPEG, and XBM graphic file formats). Netscape can interpret many other file formats with the help of external helper applications. To accommodate the file formats requiring helper applications, Netscape keeps a mapping of file formats to helper applications. MIME (Multipurpose Internet Mail Extensions) is a standardized method for organizing divergent file formats. The method organizes file formats according to the file's MIME type. When Netscape software retrieves a file from a server, the server provides the MIME type of the file. Netscape uses the MIME type to establish whether the file format can be read by the software's built-in capabilities or, if not, whether a suitable helper application is available to read the file. For servers that do not provide a MIME type with a file, Netscape interprets the file's extension (a suffix appended to a file name). For example, the .html extension in the file name index.html suggests a file in the HTML format. Likewise, a .zip extension suggests a compressed file, an .rtf extension suggests a file in the Rich Text Format, and so on. You can view and configure the mapping of all MIME types to helper applications by using the Helper Applications panel. Technical note: The panel currently lacks a Delete button and the ability to assign arbitrary values to file types. If needed, advanced users might want to edit the preferences file directly. <HR ALIGN="right"WIDTH=85%> <A NAME="C5"> Can you summarize the Usenet newsgroup screens? </A> Before you can use news for the first time you need to configure Netscape to point to your Usenet news server. Set the host name of your NNTP server in the News panel. Your newsgroup subscription information is stored in a News RC file. If you have no previous News RC file, Netscape creates one that lists a couple of newsgroups designed for new users. <DT>Subscribed newsgroups <DD>Shows a listing of all the Usenet groups that you have subscribed to and lists the number of unread articles in each newsgroup. This view also allows you to subscribe and unsubscribe to newsgroups. <DT>Server list <DD>Shows a listing of the news servers you have connected to. This view appears prior to the subscribed newsgroups view only if you have connected to multiple news servers. Otherwise, this view is doesn't appear. <DT>Newsgroup listing <DD>Shows a list of all the unread articles in a threaded format. The threaded format groups all articles that are related to each other in a compact, ordered listing. Articles that are responses to previous articles are nested under the parent articles. <DT>Article listing <DD>Shows a single article. The article listing allows you to read the article, post a reply to the newsgroup, or send a mail reply to the original poster. The article may contain links to other articles or Internet pages. <DT>Send Mail/Post News dialog <DD>Allows you to post a new article to a newsgroup, reply to an existing news article, or send mail to an e-mail address. <HR ALIGN="right"WIDTH=85%> <A NAME="C6"> Why might I use Gopher? </A> Some information on the Internet is offered through Gopher servers. When you want information that happens to be on a Gopher server, you'll click on a link whose URL begins with gopher (or enter the URL in the location field). Netscape lets you access Gopher servers in the same way you access World Wide Web (http) pages. Though Gopher pages lack rich formatting, menu listings allow you to bring content pages or additional menu sublistings. A menu is presented as a list of links, each link preceded by a small icon indicating the type of resource the link brings. For example, Gopher links can bring you: <ul> <li>menus <li>text files <li>images <li>indexes <li>movie and binary files </ul> Gopher indexes use form pages to allow you to find information on Gopher servers. An index page typically provides an editable field for you to enter a search string and a button for you to submit the form to the Gopher server. The results of the search are a Gopher menu listing items that match your search criteria. Some files, such as short digital movies, require the use of Netscape's helper applications. If available, Netscape automatically launches the helper application required by a Gopher link. <HR ALIGN="right"WIDTH=85%> <A NAME="C7"> Why might I use FTP (file transfer protocol)? </A> By clicking on a link whose URL begins with ftp (or by entering the URL in the location field), you can navigate directories, view files (including HTML and image files), and download software. Netscape lets you access FTP servers in the same way you access World Wide Web (HTTP) servers. However, you may find the FTP directory and content pages have minimal formatting. When possible, Netscape shows the type, size, date and a short description of each file in a directory. A directory is presented as a list of links, each link often preceded by a small icon indicating another directory or a file. Clicking on a directory link brings you a subdirectory. Typically, at the top of a subdirectory is link that brings you the parent directory. Clicking on a binary file or program automatically downloads the software to a folder (designated in the Directories panel) on your computer. After downloading, Netscape automatically looks for a suitable helper applicationto launch the file. If the necessary helper application is not available, Netscape presents you with a dialog box asking whether you want to save or discard the downloaded software. Not all files are downloaded using FTP. By using the pop-up menu or by clicking on a link with the shift key held down, you produce the dialog box for saving an HTTP page, an image file, or other file type to disk. <HR ALIGN="right"WIDTH=85%> <A NAME="C8"> What is a cache and how does it work? </A> A cache temporarily stores the information on a page in your computer. If you request a page that is stored in a cache, Netscape can retrieve the page from the cache more quickly than retrieving the page again from its location out on the network. The first time you ask for a page, Netscape retrieves the page from the network. No pages are permanently stored in a cache, but each page you bring is temporarily stored in a cache. If you request a page you have seen before, Netscape checks to see if the page is available in a cache. For example, if you use the Back button to bring a page, a cache can display the page more quickly than the network can retransmit it. Sometimes you may not want a page to be retrieved from a cache. The page you brought initially may no longer be identical to the page currently offered by the network. If a modification to a particular URL has occurred, you may want the updated page rather than the copy (now stale) stored in a cache. Remember, you have no control over when a server updates its pages. When you click on a link, choose a bookmark, enter a URL, or press the Reload button, Netscape checks with the server to see if an update has occurred before bringing a page from a cache. If any change to the page has occurred, a fresh version is transmitted over the network; otherwise, a copy is quickly retrieved from a cache. When you press the Back button or choose a history item, Netscape does no such check. Since you are explicitly requesting a previously viewed page, Netscape tries first to retrieve the cached copy (if still present in the cache) even if the server offers a more recent version. <HR ALIGN="right"WIDTH=85%> <A NAME="C9"> What is the difference between memory cache and disk cache? </A> Netscape supports two kinds of caches to improve performance and reduce network traffic. When you bring a page from the network, information is stored in both a memory cache and a disk cache. Netscape retrieves a page from the memory cache more quickly than from the disk cache, though retrieving from the disk cache is still faster than fetching from the network. The disk cache has the advantage of persistence. When you exit a session (quit the Netscape application), the memory cache is emptied, but the disk cache is maintained (and takes up space on your hard disk). Sometimes a cache can get confused (such as when servers provide inaccurate page modification dates). If you suspect a cache is acting improperly (such as providing stale pages) or just wish to free up space, you can clear the caches by pressing the Clear Memory Cache Now and Clear Disk Cache Now buttons in the Network panel. <HR ALIGN="right"WIDTH=85%> <A NAME="C10"> What is the recommended size for each cache? </A> You can change the size of each cache to maximize its effectiveness. A larger cache may increase Netscape performance, though allocating too much space may constrict other applications. You might try to increase the size of the memory cache to whatever your system routinely has unused and increase the disk cache to between 2,000 and 5,000 kilobytes (2 and 5 megabytes). You might find that a large disk cache increases the time required for the Netscape application to quit. If Netscape's cache maintenance causes undue delay when you exit the program, consider reducing size of the disk cache. <HR ALIGN="right"WIDTH=85%> <A NAME="C12"> Where can I learn about Internet security? </A> The Internet security technology developed by Netscape Communications to ensure private and authenticated communications (called SSL, short for Secure Sockets Layer protocol) is an open platform put into the public domain for the Internet community. Netscape Navigator and the Netscape Commerce Server are the first products to offer this nonproprietary technology. The introductory information in the Netscape Navigator Handbook, accessed via the Help menu, tells you why you need security on the Internet and how to recognize the security features built into Netscape Navigator. <HR ALIGN="right"WIDTH=85%> <A NAME="C13"> Can I safely transmit personal information such as credit card numbers? </A> You can enter your credit card number on a secure (https) Netscape Navigator form and transmit the form over the Internet to a secure Netscape Commerce Server without risk of an intermediary obtaining your credit card information. The security features offered by Netscape Communications technology protects commercial transactions, as well as all other communications, from misappropriation and fraud that could otherwise occur as information passes through Internet computers. Secure communications does not eliminate all of an Internet user's concerns. For example, you must be willing to trust the server administrator with your credit card number before you enter into a commercial transaction. Security technology secures the routes of Internet communication; security technology does not protect you from unreputable or careless people with whom you might choose to do business. The situation is analogous to telling someone your credit card number over the telephone. You may be secure in knowing that no one has overheard your conversation (privacy) and that the person on the line works for the company you wish to buy from (authentication), but you must also be willing to trust the person and the company. Server administrators must take additional precautions to prevent security breeches. To protect your information, they must maintain physical security of their server computers and control access to software passwords and private keys. <HR ALIGN="right"WIDTH=85%> <A NAME="C14"> How does Netscape's security technology protect me? </A> The security features built into Netscape Navigator and the Netscape Commerce Server protect your Internet communications with: <ul> <li>Server authentication (thwarting impostors) <li>Privacy using encryption (thwarting eavesdroppers) <li>Data integrity (thwarting vandals) </ul> Without thorough security, information transmitted over the Internet is susceptible to fraud and other misuse by intermediaries. Information traveling between your computer and a server uses a routing process that can extend over many computer systems. Any one of these computer systems represents an intermediary with the potential to access the flow of information between your computer and a trusted server. You need security to make sure that intermediaries cannot deceive you, eavesdrop on you, copy from you, or damage your communications. The Internet does not provide built-in security. The SSL protocol delivers server authentication, data encryption, and message integrity. SSL is layered beneath application protocols such as HTTP, SMTP, Telnet, FTP, Gopher, and NNTP, and layered above the connection protocol TCP/IP. This strategy allows SSL to operate independently of the Internet application protocols. With SSL implemented on both the client and server, your Internet communications are transmitted in encrypted form. Information you send can be trusted to arrive privately and unaltered to the server you specify (and no other). <HR ALIGN="right"WIDTH=85%> <A NAME="C15"> To what degree can SSL security protect me? </A> SSL uses authentication and encryption technology developed by RSA Data Security Inc. For example, Netscape Navigator's export implementation of SSL (U.S. government approved) uses a medium-grade, 40-bit key size for the RC4 stream encryption algorithm. The encryption established between you and a server remains valid over multiple connections, yet the effort expended to defeat the encryption of one message cannot be leveraged to defeat the next message. A message encrypted with 40-bit RC4 takes on average 64 MIPS-years to break (a 64-MIPS computer needs a year of dedicated processor time to break the message's encryption). The high-grade, 128-bit U.S. domestic version provides protection exponentially more vast. The effort required to break any given exchange of information is a formidable deterrent. Server authentication uses RSA public key cryptography in conjunction with ISO X.509 digital certificates. Netscape Navigator and Netscape Commerce Server deliver server authentication using signed digital certificates issued by trusted third parties known as certificate authorities. A digital certificate verifies the connection between a server's public key and the server's identification (just as a driver's license verifies the connection between your photograph and your personal identification. Cryptographic checks, using digital signatures, ensure that information within a certificate can be trusted. To evaluate the strategic and quantitative implications of the SSL implementation of certification and public key technology, consult the SSL Protocol specification via the Help/On Security menu item. <HR ALIGN="right"WIDTH=85%> <A NAME="C16"> How can I tell when security is in effect? </A> You can tell whether a document comes from a secure server by looking at the location (URL) field. If the URL begins with https:// (instead of http://), the document comes from a secure server. To connect to an HTTP server that provides security using the SSL protocol, insert the letter "s" so that the URL begins with https://. You need to use https:// for HTTP URLs with SSL and http:// for HTTP URLs without SSL. A news URL that starts with snews: (the letter "s" inserted in front of news:) is used for a document coming from a secure news server. You can also verify the security of a document by examining the security icon in the bottom-left corner of the Netscape Navigator window and the colorbar across the top of the content area. The icon consists of a doorkey on a blue background to show secure documents and a broken doorkey on a gray background to show insecure documents. The doorkey has two teeth for high-grade encryption, one tooth for medium-grade. The colorbar across the top of the content area is blue for secure and gray for insecure. A mixed document containing secure and insecure information is displayed as secure with insecure information replaced by a mixed security icon. Some servers may permit you access documents insecurely (using http://) to view mixed documents in full. More detailed security information can be found by choosing the File/Document Information menu item. Several configurable notification dialog boxes inform you when you are entering or leaving a secure space, viewing a secure document that contains insecure information, and using an insecure submission process. You'll always be warned if a secure URL is redirected to an insecure location, or if you're submitting via a secure form using an insecure submission process. <HR ALIGN="right"WIDTH=85%> <A NAME="C17"> What does the Document Information dialog box tell me? </A> Choosing the File/Document Information menu item produces a dialog box with a document's title, location (URL), date of last modification, character set encoding, and the security status of a document, Secure documents specify the type of encryption protecting the document and the version, serial number, issuer, and server subject of the certificate backing the document. <DT>Encryption Key <DD>States the type of public key supported. For example, the high-grade encryption key for U.S. domestic use only (RC4, 128-bit) refers to the 128-bit key size for the RC4 stream encryption algorithm. <DT>Subject (server id) <DD>The certification request process requires that each server administrator supply an e-mail address and certain identifying information. Identifying information may include: <ul> <li>Country (C): two-character country code <li>State or Province (ST): unabbreviated state/province name <li>Organization (O): legal, registered organization name <li>Organizational Unit (OU): optional department name <li>Locality (L): city the organization resides or is registered in <li>Common Name (CN): the server's fully qualified host name (such as: hostname.netscape.com) </ul> <DT>Issuer (certifier id) <DD>Identifies the certificate authority responsible for issuing the certification is identified. Identifying information is presented using the same abbreviations as those used to identify the server (C, for country, and so on). <HR ALIGN="right"WIDTH=85%> <A NAME="C18"> Are certificates required and where do you get one? </A> Currently, certificates are issued to organizations running servers and are not issued to Netscape Navigator users. To operate using security features, the Netscape Commerce Server requires a digitally signed certificate. Without a certificate, the server can only operate insecurely. If you are a server administrator and want to obtain a signed certificate, you need to submit a certificate request to a certificate authority, a third-party organization that issues certificates, and pay an associated service fee. Netscape Communications has engaged RSA Certificate Services, a division of RSA Data Security, Inc., to issue certificates to Netscape customers and will engage other certificate authorities over time. The process to obtain a certificate is explained in the Netscape Commerce Server manual. During the certificate request process, your server software generates a public key/private key pair and you choose a distinguished name. Online forms guide you through the process of submitting the form to RSA. RSA verifies the authenticity of each certificate request (making sure requesters are who they claim to be). The approval process helps protect you, your organization, and the certificate authority. Upon approval, RSA digitally signs the request and returns the unique digitally signed certificate to you through e-mail. You can then install the signed, valid certificate and enable security. You'll need to establish adequate precautions to maintain the integrity of the signed certificate and your private key. <HR ALIGN="right"WIDTH=85%> <A NAME="C19"> Can one certificate be used on multiple servers? </A> Technically, one certificate can be used on multiple servers, however risks are involved that would discourage this choice in many circumstances. If the same certificate is used on multiple servers, any compromise of one server's public key and private key pair endangers information on the other servers. (Certificates are protected by public and private key pairs linked by a powerful cryptographic algorithm. These keys have the ability to encrypt and decrypt information. No one else's keys can decipher messages to you encrypted with your public key. And no one else's keys can be used to pose as you by sending messages encrypted with your private key.) Similar risks would be incurred if you were to choose to secure your house, office, car, safety deposit box, and bike with the same key. You would only have to carry around a single key, but you would not have the flexibility to provide access to one item without providing access to all items. If security was compromised for one item, it would also be compromised for other items. Multiple servers that are running on the same piece of hardware can technically use the same certificate. However, as your software installations expand, the need for different levels of security and individual keys increases. The security requirements for information served at remote locations or on separate hardware are best satisfied by unique certificates. <HR ALIGN="right"WIDTH=85%> <A NAME="C20"> Do security features impose limitations on the ability to access sites? </A> The security protocol works as an adjunct to other protocols without limiting access capabilities. You can use Netscape Navigator to bring either secure or insecure documents. Nor does security limit Netscape's Usenet news or electronic mail abilities. If a document that is otherwise secure contains information that is insecure, the insecure information is replaced by a mixed security icon. However, a server may permit you to bypass this security feature by accessing the mixed security document through the insecure http protocol instead of the secure https protocol. The security aspects of SSL protect you from insecure transmissions, but do not limit your ability to receive insecure transmissions. Online forms can be secure if the submit action is an https:// URL to a secure server. Netscape Navigator uses dialog boxes to inform you about security status of the submission process when you submit a form. You can save a secure document (though secure documents are not cached to disk among sessions). You can also view the HTML source of a secure document. Security affects the transmission of a document without affecting your ability to manipulate the document. <HR ALIGN="right"WIDTH=85%> <A NAME="C21"> How can I save files and images onto my hard disk? </A> The File/Save As menu item produces a dialog box for saving a page locally (onto your hard disk) in source or text format. Source format produces a text file encoded with the HTML necessary to reproduce the formatted text or image faithfully; text format saves text without the HTML code. Whereas some links, such as many FTP links, automatically download and save a file to disk, Save As manually saves page files. You can also save a page to disk without bringing the page to screen. Position the mouse over a link or image, then click the right-side mouse button to produce a pop-up menu with the items Save this Link as and Save this Image as. These menu items produce a dialog box for saving a file. Clicking on any link with the shift key held down also produces a save dialog. Saving a file onto your hard disk allows you to display the page's information without any network connection. You can choose File/Open File to display the HTML-formatted text or graphic image of any local file saved in source format (though a page's inline images may be replaced with icons). For GIF, JPEG, or other nontext files to show up in the Open File dialog, you'll need to select "All Files". The pop-up menu item View this Image lets you see an isolated image file. The pop-up menu item Copy this Image Location copies the URL of the image file to the clipboard. Once you have the URL, you can open the image and save the image onto your hard disk in source format using File/Save As or the pop-up menu. You could also use View/View Source to find the URL of an inline image embedded in HTML code). <HR ALIGN="right"WIDTH=85%> <A NAME="C22"> What is dithering and how is it used? </A> Dithering is a software imaging process for arranging adjacent pixels of varying shades into order to achieve a visual effect. The process often enhances a computer's ability to display an image, particularly useful when the color or resolution of the original image must reproduced on computers with different display capabilities. Netscape's display of inline GIF and JPEG sometimes needs to translate an image's colors into similar colors available on your computer. If your computer doesn't have color capabilities that match the color information in an image, the image may look speckled. On Windows, you can choose radio buttons in the Images panel to Dither to Color Cube or Use Closest Color in Color Cube. JPEG images, however, are always dithered. When you choose to Dither to Color Cube, Netscape dithers the computer's available colors to most closely match the image's colors. When you choose Use Closest Color in Color Cube, Netscape substitutes an available color that most closely matches the image's colors. Images that are displayed with dithering take slightly more time to display than images using color substitution. <HR ALIGN="right"WIDTH=85%> <A NAME="C23"> How do you create hierarchical menus? </A> On Windows: <OL> <li>Choose the Bookmarks/View Bookmarks menu item to view the Netscape Bookmarks window. <li>Click on the icon above the position you want a new folder. Each folder represents a hierarchical menu header in a pull-down menu. <li>Choose Insert Header from the Items menu, type a title in the Name field, and click OK to create a new folder. <li>Drag and drop any bookmark icon on top of the new folder (or select the folder and choose the Insert Bookmark menu item. </OL> <HR ALIGN="right"WIDTH=85%> <A NAME="C24"> How do you convert hotlists to bookmarks? </A> Other browsers use hotlists similar to the way that Netscape uses bookmarks. Users of other browsers may wish to preserve the URLs they have accumulated as hotlists by converting them to bookmarks. Choose the Bookmarks/View Bookmarks menu item. On Windows, choose the File/Import menu item in the Netscape Bookmarks window. These commands read any HTML file containing links and convert the links into bookmarks. To import a hotlist into Netscape, you should first convert your hotlist to HTML. Several downloadable utilities perform this conversion. You may also be able to use another browser's mail command to transmit a hotlist in HTML format. <HR ALIGN="right"WIDTH=85%> <A NAME="C27"> Are there any Windows-specific tips or tricks? </A> <DT>Using Netscape without a network connection <DD>To use Netscape to browse local files without maintaining a network connection, you should get the file mozock.dll. By installing this file as winsock.dll, you can use the menu item File/Open File to view local files on your hard disk (or use the location field to type in a DOS pathname). <DT>Registry versus netscape.ini <DD>The 32-bit version uses the system registry instead of a netscape.ini file. To manually edit preferences, run regedit.exe. For the 16-bit version: Netscape looks in win.ini in the section <PRE> [Netscape] ini= </PRE> for the location of the netscape.ini file (the INI file contains initializations and preference settings used internally by Netscape). If the file doesn't exist, Netscape looks for the file in the directory where the application runs. Also: You may be able to copy your INI file from other browsers to the netscape.ini file. Be sure to add fields for History File and File Location, and to convert hotlist entries to Netscape bookmarks. <DT>Viewing HTML source documents <DD>To use Netscape (rather than an external viewer) as the HTML source viewer, leave the View Source field blank in the Options/Preferences/Applications panel. <DT>Shortcut for cycling among open Netscape windows <DD>Press the Crtl and Tab keys together to consecutively bring to the front each open Netscape window. <HR ALIGN="right"WIDTH=85%> <A NAME="C38"> What are Windows 95 Internet shortcuts? </A> Internet shortcuts enable you to double-click on a desktop icon to open Netscape with a particular page automatically loaded. The desktop icon functions as a stand-alone bookmark, opening the Netscape application (if necessary) and bringing to the screen the page whose URL is stored as part of the shortcut. Internet shortcuts are only available on the Windows 95 version of Netscape. To create an Internet shortcut for any page, press the right mouse button to display the pop-up menu and select the Create Shortcut item. This displays the Create Internet Shortcuts dialog box containing a Description field, a URL field, and a check box. By default, the Description field is preset with the words Shortcut to followed by the title of the page you are viewing and the URL field is preset with the the page's URL. You can modify the contents of either field to specify any page you wish. If the Place on Desktop check box is checked when you create the Internet shortcut icon, the icon appears on the desktop; otherwise, the icon appears in the Netscape folder. Click the OK button to create the Internet shortcut. You can also create an Internet shortcut for a particular page by clicking on a link to the page, then dragging and dropping the link onto the desktop. Once you have created the Internet shortcut icon, you can drag and drop the shortcut icon (like a bookmark) onto the Netscape window to automatically open the shortcut page. Even if the Netscape application is not running, you can drag and drop the shortcut icon on top of the Netscape application icon to open Netscape and with the shortcut page automatically loaded. <HR ALIGN="right"WIDTH=85%> <A NAME="C29"> What is the World Wide Web's place in the Internet? </A> World Wide Web (WWW or Web) is one facet of the Internet consisting of client and server computers handling multimedia documents. Client computers use browser software (such as Netscape Navigator) to view documents (pages). Server computers use server software (such as the Netscape Commerce Server) to maintain documents for clients to access. Web documents are created by authors using a language called HTML (HyperText Markup Language) that offers short codes (also called tags) to designate graphical elements and links. Clicking on links brings documents located on a server to a browser, irrespective of the server's geographic location. Documents may contain text, images, sounds, movies, or a combination. Documents are addressed with a URL (Uniform Resource Locator or, for short, location). Clients and servers use a document's URL to find and distinguish among documents. <HR ALIGN="right"WIDTH=85%> <A NAME="C30"> How can I access the Internet? </A> Some companies maintain a network that is linked to the Internet via dedicated communication lines. Those with less substantial resources, including most individuals, access the Internet via a service provider. A service provider is a company that offers use of its dedicated communication lines. If you have a modem, you can dial up a service provider whose computers will connect you to the Internet, typically for a fee. Dial-up access means that the modem on your computer can log in to another computer that is hooked up to the Internet. The most popular dial-up access alternatives are shell accounts and SLIP/PPP accounts. When using a shell account, you dial into a service provider's computer and use the UNIX operating system to indirectly connect to the Internet. With an indirect connection, your computer does not interact with Internet computers. For example, if you download a file from an Internet site, the file is saved on the service provider's computer rather than on your computer. You then have to transfer the file from the service provider's computer to your home system. Shell accounts, while limited in features, have historically been less expensive than direct access accounts. When using a SLIP or PPP account, you dial into a service provider's computer and run applications that directly connect to the Internet. With a direct connection, your computer can use browsers with user-friendly graphical interfaces to interact with Internet computers. A direct connection lets you download files directly to your system from remote sites. SLIP or PPP access to the Internet offers more performance and convenience than a shell account. <HR ALIGN="right"WIDTH=85%> <A NAME="C31"> What are SLIP and PPP? </A> SLIP, short for Serial Line Internet Protocol, and PPP, short for Point-to-Point Protocol, are Internet standards for transmitting Internet Protocol (IP) packets over serial lines (phone lines). Internet information is packaged into IP packets, a method for enclosing data into small, transmittable units (wrapped up on one end, unbundled on the other). A service provider may offer SLIP, PPP, or both. Your computer must use connection software (usually provided by the service provider) that matches the protocol of the server's connection software. PPP is a more recent and robust protocol than SLIP. <DT>CSLIP <DD>CSLIP, Compressed Serial Line Internet Protocol, is a version of SLIP that supports compression. <DT>Dynamic SLIP and Static SLIP <DD>When you use a SLIP or PPP connection to the Internet, your service provider's server identifies your computer by providing you with an IP address (a number like 192.34.32.81). Using dynamic SLIP, your computer is dynamically allocated a temporary IP address (just for the immediate session) from a set of IP addresses maintained by the server. Using static SLIP, your computer is allocated a one-time, permanent IP address (when your account is set up) for use in all your sessions. Static SLIP means you have a static IP address. <HR ALIGN="right"WIDTH=85%> <A NAME="C32"> What are TCP/IP and Winsocks? </A> <DT>TCP/IP <DD>TCP/IP, short for Transmission Control Protocol/Internet Protocol, is the standard communications protocol required for Internet computers. To communicate using TCP/IP, PCs need a set of software components called a TCP/IP stack. <DT>TCP/IP Stack <DD>Only the PC platform requires a TCP/IP stack. To make a successful connection to the Internet, your PC needs application software such as Netscape plus a TCP/IP stack consisting of TCP/IP software, sockets software (Winsock.DLL), and hardware driver software (packet drivers). Several popular TCP/IP stacks are available for Windows, including shareware stacks. <DT>Winsocks <DD>Winsock stands for Windows Sockets. Winsocks is a set of specifications or standards for programmers creating TCP/IP applications (communicating applications such as Netscape) for Windows. <HR ALIGN="right"WIDTH=85%> <A NAME="C33"> What should I know about firewalls? </A> A firewall protects one or more computers with Internet connections from access by external computers connected to the Internet. A firewall is a network configuration, usually created by hardware and software, that forms a boundary between networked computers within the firewall from those outside the firewall. The computers within the firewall are a secure subnet with internal access capabilities and shared resources not available to the computers on the outside. Often, a single machine atop the firewall is allowed access to both internal and external computers. Since the computer atop the firewall is directly interacting with the Internet, strict security measures against unwanted access from external computers are required. A firewall is commonly used to protect information such as a network's e-mail and data files within a physical building or organization site. A firewall reduces the risk of intrusion by unauthorized people from the Internet, however the same security measures may limit or require special software for those inside the firewall who wish to access information on the outside. A firewall can be configured using proxies (and/or SOCKS) to designate access to information from each side of the firewall. <HR ALIGN="right"WIDTH=85%> <A NAME="C34"> What are proxies and SOCKS? </A> <DT>Proxy or proxy server <DD>A proxy allows access to the Internet from within a firewall. A proxy is a special server that typically runs in conjunction with firewall software. The proxy server waits for a request from inside the firewall, forwards the request to the remote server outside the firewall, reads the response, then sends the response back to the client. Netscape lets you set the name and port number of proxy servers in the Options/Preferences/Proxies panel in order to resolve requests for access to Internet resources. Protocols such as HTTP, FTP, Gopher, WAIS, and Security can have designated proxies. Proxies may be preferred over SOCKS for their ability to perform caching, high-level logging, and access control. <DT>SOCKS <DD>SOCKS is software that allows computers inside a firewall to gain access to the Internet. SOCKS is usually installed on a server positioned either inside or on the firewall. Computers within the firewall access the SOCKS server as clients to reach the Internet. Netscape lets you set the name and port number of the SOCKS host (server) in the Proxies panel. On Windows, the host is specified in the registry (32-bit) or INI file (16-bit). Sometimes you need to restart Netscape after changing the SOCKS host. Netscape supports version 4 of SOCKS defined by the socks.cstc.4.1 implementation. <HR ALIGN="right"WIDTH=85%> <A NAME="C35"> How do server push and client pull work? </A> Generally, pages are brought to your screen as a result of your input. You click on a link or an image to request a page. But servers also have the ability to deliver an updated version of a page to your screen automatically. For example, a weather watcher might want to see an updated satellite photo at 15-minute intervals. Netscape provides the pages creators and server administrators two complementary tools for making this work. <DT>Server push <DD>the server transmits page information to your screen. The Netscape applications displays the information and leaves the connection to the server open. With an open connection, the server can continue to push updated pages for your screen to display on an ongoing basis. You can close the connection by closing the page. <DT>Client pull <DD>the server transmits page information to your screen along with programming code that automatically instructs the Netscape application to perform an action such as "reload this page in ten minutes" or "go load this URL in two minutes". After the specified amount of time has elapsed, the client (the Netscape application on your computer) pulls updated pages to your screen according to the instructions it has been provided along with the page. You can terminate the page's actions by closing the page. In server push, a HTTP connection is held open for an indefinite period of time (until the server is finished sending data to the client or until the client interrupts the connection). In client pull, a HTTP connection is never held open; rather, the client is told when to open a new connection and what data to fetch. Server push uses a variant of the MIME message format "multipart/mixed" that lets a single message (or HTTP response) contain many data items. Client pull uses an HTTP response header (or equivalent HTML tag) that tells the client what to do after a specified time delay. <HR ALIGN="right"WIDTH=85%> <A NAME="C36"> What are MIME, Types files, and Mailcap files? </A> MIME is short for the Multipurpose Internet Mail Extensions protocol. This protocol is used in Internet communications to transmit documents of varying formats. The protocol handles complexities by establishing a relationship (a mapping) between the format of a document's content and the format of the document's computer representation. Applications using MIME can establish the type of software necessary to interpret the content of a transmitted document. With the proper Helper Application settings and software, Netscape can automatically initiate the necessary actions to provide you access to content transmitted in numerous formats. On Windows, the mapping of MIME types is handled in the Helper Applications panel. As an example, an audio file mySound.au plays using the audiotool application. <HR ALIGN="right"WIDTH=85%> <A NAME="C37"> How do I learn to write HTML and publish pages? </A> You can write HTML (HyperText Markup Language) pages using any word processor or text editor. (To publish pages on the Internet, you need to submit your pages to a server computer using server software.) HTML uses embedded codes (tags) to designate graphical elements and links. These codes can be produced simply from your keyboard using angled brackets and the slash character. For example, the tag presents text in bold letters. An HTML source file containing the expression This stands out. is displayed on screen in bold. Notice that the tag is required to notate the end of the bold expression. HTML consists of many such tags, including tags for big headlines, underlining, italics, titles, and paragraph breaks. Netscape also supports tags that allow you to create tables and custom backgrounds. Consult Netscape's online pages to learn how to take advantage of these features. One feature you'll certainly want to use is the HTML link. Here's example HTML that creates a link for users to click on: <PRE> <A HREF="http://www.worldnet.att.net/">Home</A> </PRE> The part of the tag between quotation marks is the URL of the page that clicking on the link brings. The text following the URL contains the highlighted text (Home) the user sees on screen. The tag coding and brackets are also a required part of the link. The method to insert images in your pages in very similar to that of inserting links. Inline images are links to image files. To see any one page's HTML source, you can choose the View/Source menu item. This command displays the text and tags used to create the content and content style of the current page. <A HREF="../index.htm">Netscape Handbook: Table of Contents</A> <HR SIZE=4> <A HREF="mailto:info@netscape.com">info@netscape.com</A> Copyright © 1994, 1995 Netscape Communications Corporation.