Site map pages: most web site maps are ordinary web pages with lists of links to the major elements of your web site (fig. 5.10). These master lists of the major pages in your site are an excellent resource for search engine crawlers, and site map pages are a great way to ensure that every important page of your site is linked in a way that search crawlers and users can easily find. Site map or “index” pages are a common element of web sites, and users who prefer to browse through lists of links know to look for site map or index pages in a well-organized site. In the earlier days of the web you’d see site maps that were laid out as diagrammatic charts or visual maps of the site, but the highly visual site map metaphors have largely faded in favor of the much more efficient link lists.
xml site maps for search engines: the second common meaning for “site map” refers to a text file in xml format that sits at the level of your home page and informs web search crawlers about the major pages in your web site, how to find the pages, and how often the pages are likely to be updated (daily, weekly, monthly)