One of the neat things I came across while working on my current project is an ajax shortcut for hooking in to the Sys.Application.load event on the client. As it turns out you can declare simply declare a pageLoad function which AJAX will automatically call. Further details can be found here in the AJAX documentation.

function pageLoad(sender, args)
{
     //called on Sys.Application.load
}
 
function pageUnload(sender, args)
{
     //called on Sys.Application.unload
}
Note: You can also do the same for the Sys.Application.unload event.