body onload - gets removed

Hi All
I'm using Visual Studio 2010 and creating a ASP.net web site using C#.  
I have the following code in my page:-
 
<body onload= "initialize()";>  
but alot of the time the onload= "initialize()" gets removed and reverts to
 
<body>  
This is very annoying.
 
Any ideas why this is happening?
 
tia
Andrew
 
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