Following up on the recently posted tip, a crucial reason for implementing URL rewriting is to make a site compliant with search engines.
Typically, dynamic content such as product displays on a shopping site, articles on a news/community site, or other content-rich site will be stored in a database and dynamically displayed.
Pages with dynamic content will use a query string structure such as http://www.mysite.com/displayid.aspx?productid=287
Virtually all search engines will not index webpages that include dynamic content. More specifically, when the search engine spider or “bot” visits your site to scan the pages it will skip any page that has a “?” (the query string parameter marker).
The only solution is to use a URL rewriting application or utility that will create “virtual URL's” by removing the query string “?” and returning different URL.
In addition to commercial application the http modules in ASP.NET make it straightforward to implement yourself.
For examples, see http://www.codeproject.com/aspnet/urlrewriter.asp or