Script Manager in asp.net

Hi,
RadScriptManager and ScriptManager both are probably same.
Take RadScriptManager in all three master pages. And if required then take RadScriptManagerProxy in content pages.
 
If you have the script manager in your master for instance which will go across all pages but you want a script manager reference in an underlying page or user control. In that instance you can add multiple proxies. If you added another script manager then you'll get the error on the page
 
--Amit