To Use it in ASP.NET fallow the steps:

1. Open VS2008

2. Create new page default.aspx

3. Create new page asdf.htm

3. Open webconfig file and then writer code in <configuration> in <system.web></System.web>

<urlMappings enabled="true">
 <add url="~/Default.aspx"  mappedUrl="~/asdf.htm" />
 </urlMappings>

4. Now open default.aspx it will open asdf.html

Thanks