A SiteMap is a way to describe the pages of your site to a search engine. It also provides the mechanism for letting search engines know when your pages have been added, removed or otherwise modified. A SiteMap file is an XML formatted file containing an entry (or item) for each page of your site. Each item also contains the date/time the page was last modified. The exact formatting of the XML file varies depending on which search engine it is tailored for; however, very soon we should have a unified “SiteMaps protocol” to be used for the big 3 (Google, Yahoo!, and Microsoft). This means you will have a single SiteMap XML file to maintain and all 3 search engines will pull from it! More about SiteMaps can be learned from the official website: http://www.sitemaps.org.
So how does SharePoint deal with SiteMaps? You will still need to tell each of the big 3 about your SiteMap file by registering it and verifying you are who you say you are (this is a painless process taking about 5 minutes). This will only need to be done once. Prior to registering your SiteMap, you will need to actually have a SiteMap file. Here’s where MOSS will save you big time. Instead of manually updating your SiteMap file every time something on your MOSS site changes, you should simply add on a custom control that does this for you. It should automatically update your SiteMap file when a public facing page is published to a major version. We will post this control along with its source code (un-supported of course) very soon.