It seems that you have installed IIS after visual studio.
If this is the case, run aspnet_regiis to register your IIS with ASP.Net.

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Wajahat Abbas
http://www.wajahatabbas.com
> I try to open a project , and get the following message:
> "open the application because the web server on this computer is not
> running. Start the web server before proceeding".
> I went to the administative tools -> internet information services -> web
> sites >
> default web site -> and activated "start". It won't work !