HTTP Error 404.3 - Not Found - How to fix it

The page your are requesting cannot be served because of the extension configuration. If the page is a script, add a handler. If the file should be downloaded, add a MIME map

How to fix it:

1.  Add a handler

2.  Add MIME map

Solution:
Go to START ->
Default Programs ->
Programs and Features ->
Turn Windows ON or OFF ->
Internet Information Services ->
World Wide Web Services ->
Application Development Features -> and Check ASP.NET

Hope this is helpful!