http://msdn2.microsoft.com/en-US/library/e8z01xdh(VS.80).aspx

To enable debugging in the project properties

In Visual Studio 2005, use the <Project> Property Pages to set project properties for Web application debugging by doing the following:

1.      Open the Property Pages by right-clicking the project name in Solution Explorer, and selecting Property Pages.

2.      Click the Start Options tab.

3.      Under Debuggers, make sure the ASP.NET box is selected.

To enable debugging in the web.config file

<compilation debug="true" >

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