What is the purpose of the global.asax in Asp.net?
Some application level events you can declared ..
For Example , you want to execute something while All session ends for that you can you global.asax file straight way .. There is a event Session_End
If you mean global.asax, then open it up and look inside. What do you see there?
The Global.asax file, also known as the ASP.NET application file, is an optional file that contains code for responding to application-level and session-level events raised by ASP.NET or by HTTP modules. The Global.asax file resides in the root directory of an ASP.NET application. At run time, Global.asax is parsed and compiled into a dynamically generated .NET Framework class derived from the HttpApplication base class. ASP.NET is configured so that any direct URL request for the Global.asax file is automatically rejected; external users cannot download or view the code in it. The Global.asax file is optional. You create it only if you want to handle application or session events.
(MSDN, accessed on 07/06/2009 http://msdn.microsoft.com/en-us/library/2027ewzw.aspx)