Use this tab to customize Web service extensions such as ASP, PHP, PERL and etc.. By default, in order to take a more proactive stance against malicious users and attackers, IIS serves only static content - meaning features like ASP, ASP.NET, etc. do not work unless enabled. If you do not enable this functionality after installing IIS, IIS returns a 404 error.
1 ) Open Web Site Properties page
2 ) Select Extension Tab
3 ) Select required extensions to enable
4 ) Click Update button.