I faced a problem to call 2 methods at the same time from body. and the solution is very simple. I wrote a script block at the end of the page look like that.
<SCRIPT LANGUAGE=”JAVASCRIPT”>
if(document.body.onload)
{
var existingOnLoad = document.body.onload;
document.body.onload = function()
{
existingOnLoad();
MyOwnMethod();
}
}
</SCRIPT>

