Debugging SharePoint Solutions

You are using Visual Studio 2010 on a SharePoint 2010 site and get an error when hitting F5 to begin debugging....
The debugger may fail to start and complain that the web.config could not be loaded with the error message: “Could not load the Web.config configuration file. Check the file for any malformed XML elements, and try again. The following error occurred: The given key was not present in the dictionary.”
Make sure the URL assigned to the Default zone for the Web Application’s Alternate Access Mappings matches the Site URL of the SharePoint project in Visual Studio. Using one of the other zones (like Intranet) for the URL will not work. The Default Zone and the project’s Site URL need to match.