A sitemap provides an easy way for both humans and search engines to reference pages of your
web site from one central location. Usually, the sitemap enumerates all, or at least the important,
pages of a site. This is beneficial for humans in that it can be a navigational aide, and for search
engines, because it may help a web site get spidered more quickly and comprehensively.
In this chapter you learn about:
The two types of sitemaps: traditional sitemaps and search engine sitemaps.
The Google XML sitemaps standard.
The Yahoo! plaintext sitemaps standard.
The new sitemaps.org standard — soon to be implemented by all search engines.
You’ll implement PHP code that generates both Google and Yahoo! search engine sitemaps pro-
grammatically. But first, this chapter starts at the beginning and talks about traditional sitemaps.
A traditional sitemap is simply an HTML web page that contains links to the various pages of your
web site. Typically the traditional sitemap breaks down the referenced pages into groupings for easy
reading. This kind of sitemap is generally designed to assist humans in navigating, but search engine
marketers realized early on that it had a beneficial side effect of helping spiders to crawl a site.
Historically, search engines did not crawl very deeply into a web site, and it helped to link pages
located deeper in the site hierarchy (that is, one must traverse many pages to arrive there) from a
sitemap page. Today, that particular problem is
squashed (search engines now do a much
better job at crawling more deeply), but a sitemap may still assist in getting such pages spidered
faster. It may also improve their rankings somewhat by providing an additional internal link.
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