I hate forums with a bunch of unanswered questions.

In your web.config file, go to the section that looks like this:

Turn the mode to "Off" to see a detailed description of the error.

Thanks for this.

When I turn off the mode to see the detailed error, the error that came out was: Thanks for this.

An error has occurred while establishing a connection to the server.  When connecting to SQL Server 2005, this failure may be caused by the fact that under the default settings SQL Server does not allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified)

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Data.SqlClient.SqlException: An error has occurred while establishing a connection to the server.  When connecting to SQL Server 2005, this failure may be caused by the fact that under the default settings SQL Server does not allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified)

Source Error:

Line 6:      Sub Application_Start(ByVal sender As Object, ByVal e As EventArgs)
Line 7:          
Line 8:          If (Not Roles.RoleExists("Administrators")) Then
Line 9:              Roles.CreateRole("Administrators")
Line 10:         End If