HTTP 404. The resource you are looking for (or one of its dependencies) could have been removed

Hi,
The relevant project has been deployed fine in the server but when it is being called by one other project, I got this. Why?

Server Error in '/App11' Application.
--------------------------------------------------------------------------------


The resource cannot be found.
  Description: HTTP 404. The resource you are looking for (or one of its dependencies) could have been removed, had its name changed, or is temporarily unavailable.  Please review the following URL and make sure that it is spelled correctly.

 Requested URL: /App11/Detail.aspx


--------------------------------------------------------------------------------
Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.18044