When you create a Web Application in Microsoft Visual Studio .NET and then you use Windows Server 2003 with Internet Information Services (IIS) 6.0, you may receive the following error message:

The default Web access mode for this project is set to file share, but the project folder at 'Project URL' cannot be opened with the path 'Physical Project path'. The error returned was:

Unable to create Web project 'Project Name'. The file path 'Physical project path' does not correspond to the URL 'Project URL'. The two need to map to the same location. HTTP Error 404: Not Found

WHY?

Internet Information Services 6.0 blocks all requests with extensions that are not explicitly mapped in IIS. Microsoft Visual Studio .NET writes a file to the server with the .tmp extension and then requests that file back with an HTTP call to test the URL. IIS 6.0 blocks the .tmp file because .tmp files are not mapped. The call fails, and then you receive the File Not Found error message.

How to fix it?

To resolve this problem, add a MIME type for the .tmp file in IIS. To do so, follow these steps:

1. In Control Panel, open Administrative Tools, and then double-click Internet Information Services.
2. Expand the (local computer) node, and then expand Web Sites. 
3. Right-click Default Web Site, and then click Properties.
4. In Default Web Site Properties, click the HTTP Headers Tab.
5. Click MIME Types. In MIME Types, click New to register a file extension.
6. In the Extension textbox, type .tmp . In the MIME Type textbox, type temp.
7. Click OK.