URL rewriting is something that can dramatically increase search engine traffic on an ASP.NET website by elliminating the myriad of query strings that can distort the URLs of the application.
In my article on URL rewriting I write about how you can rewrite URLs using ASP.NET 2.0 and 3.5 to improve search engine results (SEO) using a variety of methods including global.asax, HTTP Modules, and HTTP Handlers. Each method has its advantages and disadvantages depending on the application.
The article shows how we can implement complete URL rewriting using a handler without all the unfortunate side effects of the postback reverting to either the unfriendly page or containing any query string parameters.
Read about it on the code project at http://www.codeproject.com/KB/aspnet/URL-Rewriting-in-ASPNET.aspx