HTML Author checks your URLs for correct syntax. Common reasons for the Invalid URL warning are the use of backslashes (\) instead of forward slashes (/), mistyping the :// delimiter, or accidentally typing a comma instead of a period in a domain name, e.g. www,adobe.com instead of www.adobe.com. Many URLs have this syntax:
Relative, or partial, URLs are allowed. This special form of URL addressing enables you to refer to files that lie above you in the directory hierarchy, without having to explicitly provide a full pathname for those files. Instead, you provide a partial pathname using a special dot notation that indicates where the named file or directory is, relative to your current position. This is particularly useful when you know where a particular directory is in relationship to the directory you're working in, and the two directories always maintain that same (spatial) hierarchical relationship.
For example, all the GIF files that you refer to might be in a directory named GIF that is two levels up from where your current is located. For example, if your URL points to a file named gif_1 within that directory, you can refer to that file as ../../GIF/gif_1. This says, in essence, to look for this file within the directory named GIF that is two levels up from the location of the document you're working on, which contains this URL.
If you type an invalid URL, it will be highlighted starting at the first invalid character. This helps you to identify the syntax error, and enables you to directly enter a replacement for the highlighted text.
Please note: This version of HTML Author does not check on the Internet to see if URLs actually exist. What it does check is that you have followed the rules for forming correct URLs.
Following is a list of the URL prefixes available on the Link Type pop-up menu of the Create Links pane, together with a brief description of the Internet service referenced by each prefix.
afs:// ANDREW FILE SYSTEM The Andrew File System is a distributed network file system for UNIX. It allows files on all AFS machines on the Internet to be grouped into a single directory structure accessible from each of these machines. URLs beginning with afs:// can be used to access files using this directory structure.
cid: CONTENT IDENTIFIERS This prefix is similar to the mid: prefix for accessing electronic mail messages (see below). The difference is that cid: is used to access specific body parts of MIME messages. MIME stands for Multipurpose Internet Mail Extensions and is a standard for the inclusion of various types of data other than ASCII text in a mail message. MIME messages are divided into body parts with content identifiers to distinguish them. URLs constructed from the cid: prefix include content identifiers to access the required body part.
ftp:// FILE TRANSFER PROTOCOL This is a commonly used protocol for retrieving files over the Internet. After the prefix is your user and password information (which can be excluded if anonymous ftp access is allowed), followed by the server name, an optional port specification, and the path leading to the file of interest.
gopher:// GOPHER PROTOCOL The Gopher service provides access to files or directories in various formats using various search techniques. The gopher:// prefix is followed by the server name, an optional port specification, and then a combination of resource identifier codes (single- digit numbers identifying the type of resource) and selector strings (directories, filenames, or search information).
http:// HYPERTEXT TRANSFER PROTOCOL The hypertext transfer protocol was specifically designed for World Wide Web use, and is the most widely used service for hypertext links in HTML documents. It can be used to retrieve and display information in a variety of ways, ranging from direct file retrieval to complex searches. The http:// prefix is followed by the server name, an optional port specification, the file path, and an optional search script, in that order.
http://www. HTTP ON WORLD WIDE WEB SERVER This additional form of the http prefix has been included because it is a popular convention to start World Wide Web server names with www.
mid: MESSAGE IDENTIFIERS A URL with this prefix can be used to hyperlink to a stored electronic mail message by specifying its unique message ID.
mailto: ELECTRONIC MAIL By appending an email address to this prefix, you will create a URL that allows electronic mail to be sent when a hyperlink with this URL is clicked in browsers with mail support. You must replace any % symbols in the email address with %25 when forming the URL, as the % character has a special interpretation in URLs.
news: USENET NEWS URLs with this prefix can be used to reference Usenet newsgroups or specific articles.
nntp: NETWORK NEWS TRANSFER PROTOCOL This is an alternate way of accessing Usenet newsgroups and articles that requires specification of an NNTP server from which to obtain the information.
prospero:// PROSPERO DIRECTORY SERVICE The Prospero file system is a virtual distributed file system, meaning that each user can set up custom directory structures independent of the actual machines and directories in which the relevant files reside. The prospero:// prefix can be used to access resources via the Prospero file system.
rlogin:// REMOTE LOGIN A URL with this prefix can be used to designate an interactive session with a remote host computer. The URL provides information about the host machine as well as the user name if required.
telnet:// TELNET This is similar to the rlogin prefix, and is for interactive sessions through a Telnet link to a remote computer.
tn3270:// TELNET WITH 3270 EMULATION This is a version of the Telnet service designed for connecting to machines that require IBM 3270 terminal emulation.
wais:// WIDE AREA INFORMATION SEARCH The WAIS service is designed for searching databases over the Internet. URLs of this type specify the server, the WAIS database to search, and the search criteria or document to be retrieved.
