Sometimes, your website doesn't load .inc files like footer.inc of your ASP .net website.The .inc is a part of #include directive used to create functions, footer, or element which is reused on multiple pages on your website.

It is necessary to add ServerSideInclude IIS handler mapping so that .inc files can load properly on website elements like header and footer.

Please following the below steps to add ServerSideInclude IIS handler mapping at IIS:

1. Login into your windows server via RDP.
   
   
2. Open IIS Manager and browse to your website.
   
   
3. Click on Handler Mappings.
   
   
   
   
4. There will be action bar at the top right corner.Click on Add Module Mapping.
5. set following parameters and click OK.
   
   Request Path = *.htm
   Module = ServerSideIncludeModule
   Name = SSI-htm
   
   
   
   
6. Click OK.

Once the above handler mapping is added, the server will start serving include files .inc and header, footer elements will look properly.