ERROR: Unable to start debugging on the web server. you do not have permission to debug the application. the URL for this project is in the Internet..

If you are running .NET Framework 1.1 and 2.0 together on the same machine, you might get this error when you try to run .NET 1.1 web application in debug mode:

"Unable to start debugging on the web server. you do not have permission to debug the application. the URL for this project is in the Internet zone."

It's easy to fix, just follow these steps:
1. Go to "Administrative Tools" and open "Internet Information Services(IIS)" .
2. Right click on "Default Web Site" and choose "Properties" option.
3. Select ASP.NET tab.
4. Look for ASP.NET version drop down and Change ASP.NET version from 2.0.xxx to 1.1.xxx.
5. Click Apply button.
6. Click Ok button.
7. Restart your IIS.

Try now opening your web project, there should not be a problem.