2010 aspx wiring together problem

I have a C# asp.net 2010 webform page that I am developing and I have the following two questios:

The following is the line of code I am referring to;

<%@ Page Title="" Language="C#" MasterPageFile="~/Rpt.Master" AutoEventWireup="true" CodeBehind="Atts.aspx.cs" Inherits="Rpt.WebForm3" %>

When I first setup the new webform page, I used the default name of WebForm3 for awhile. After starting to work with the markup file, I renamed the WebForm3 files to Atts in solution explorer. Now the line of code that says

Inherits="Rpt.WebForm3"

will not allow the web page to work if I change the "Rpt.WebForm3" to ="Rpt.Atts".

I do not see a WebForm3 file in the solution file.

1. What could I be doing wrong? Could something be 'wired together' wrong?

2. When the application does not run, I do not know where to check for the real error message that happens? Is there a file a brakpoint spot I should set to see where the problem comes from. What I see is the generic error message in the web config file that displays the final default error message if nothing is runnning.