There are two level of asp.net debugging

1. Page level debugging

For this we have to edit the page level debugging enable the trace to true in the line in the html format of the page.

%@ Page Language="vb" trace="true" AutoEventWireup="false" Codebehind="WebForm1.aspx.vb" Inherits="WebApplication2.WebForm1">

2. You can enable the debugging in the application level for this

Edit the following trace value in web.config file

Enable trace enabled=true.