If you are using URL Routing in your ASP.Net project (I’ve already covered how to do it in another article) and want to deploy the project to a machine that is running IIS 6.0 (XP or Server 2003), you’ll need to add new application extension mapping before URL routing will work.
To add new application extension mapping for URL routing, open website / virtual directory properties and click on configuration on the main tab.
Then click on Insert in Wild card application maps section (lower section). For executable path enter C:\WINNT\Microsoft.NET\Framework\v4.0.30319\aspnet_isapi.dll (if your Windows directory is different, modify the path accordingly) and uncheck option Verify that file exists. Click on OK to add new mapping.
This is all you need to do. Your website will now be able to resolve URLs that you have set up through URL routing.