window.onload = function(){
	// IE
	if(document.all){
	var margin_top = document.body.clientHeight;
	}

	// NN
	else if(document.layers || document.getElementById){
	var margin_top = innerHeight;
	}
	
	if(margin_top > 600){
	var margin_top = margin_top - 600;
	var margin_top = margin_top + 'px';
	document.getElementById('left_menu').style.marginTop = margin_top;
	document.getElementById('right_menu').style.marginTop = margin_top;
	}
};