var el=0;
function absTop(el) {
	 return (el.offsetParent)? 
	 el.offsetTop+absTop(el.offsetParent)-3 : el.offsetTop;	 
}

function update_navi() {
	myoffset = absTop(document.getElementById('mainnavihi'));
	myoffset = myoffset - 92;
	document.getElementById('subnavi').style.paddingTop = myoffset+"px";		
}
update_navi();