Labels:hakham | laptop | monitor | plant | road | sky OCR: 376 SECTION CHAPTER 7 High performance Web crawlers can visit hundreds of millions of Web pages a day Those pages, however, are only fraction of the Web. Researchers estimate that the most extensive search engines cover less than 20% of the Web. Each search engine seems focus on a slightly ferent collection of Web sites. The same search entered into different search engines can produce different results so it is sometimes worthwhile to try alternative search engines Web crawlers typically op you gather material from the invisible Web which encompasses pages that require password protected logins and pages that are dynamically generated with server- -side scripts. The potential volume of dynamically generated pages, such as all the possible pages that Amazon. .com could generate from its in ...
