If you are getting error message such as Login failed for user 'IFC\WIN50XX$', that means your connection string is wrong.
1) Remove 'Integrated Security=True;' in your connection string. This is a common problem when someone copy their site from their local machine to our server.
2) Check your connection string against the one that's given in your hosting control panel -> Database Manager -> MSSQL Manager -> Connection String. Make sure they are the same.