ASP.net and ATL Server debugging - IIS 7

Cause:

Error while trying to run project: Unable to start debugging on the web server. The server does not support debugging of ASP.NET or ATL Server applications. Run setup to install the Visual Studio .NET server components. If setup has been run, verify that a valid URL has been specified.


You may also want to refer to the ASP.NET and ATL Server debugging topic in the online documentation. Would you like to disable future attempts to debug ASP.NET pages for this project?

Posible reson is to have in-compatile web.config after converting asp.net 3.5 application to asp.net 4.0 application.

Example: having modules and httpModules in the same web.config

<configuration>
  ...
  <system.web>
    ...
    <httpModules>
      <add name="SEOModule"
         type="WebSphere.Ngate.SEOModule.SEOModule, WebSphere.Ngate.SEOModule" />
    </httpModules>
  </system.web>
  <system.webServer>
    <modules>
      <add name="SEOModule" preCondition="managedHandler"
         type="WebSphere.Ngate.SEOModule.SEOModule, WebSphere.Ngate.SEOModule" />
    </modules>
    ...
  </system.webServer>
</configuration>

Removing httpModules section will resolve the problem

<configuration>
  ...
  <system.web>
    ...
  </system.web>
  <system.webServer>
    <modules>
      <add name="SEOModule" preCondition="managedHandler"
         type="WebSphere.Ngate.SEOModule.SEOModule, WebSphere.Ngate.SEOModule" />
    </modules>
    ...
  </system.webServer>
</configuration>