A spider is a program that automatically fetches Web pages. Spiders are used to feed pages to search engines. It's called a spider because it crawls over the Web. Another term for these programs is webcrawler.

Because most Web pages contain links to other pages, a spider can start almost anywhere. As soon as it sees a link to another page, it goes off and fetches it.

Hope this helps.
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Queen JJ
www.queenjawjaw.com
All Things Royal - 2010 and Beyond
Humorist for the NABBW