function GetInnerSize () {
	var x,y;
	if (self.innerHeight) // all except Explorer
	{
		x = self.innerWidth;
		y = self.innerHeight;
	}
	else if (document.documentElement && document.documentElement.clientHeight)
		// Explorer 6 Strict Mode
	{
		x = document.documentElement.clientWidth;
		y = document.documentElement.clientHeight;
	}
	else if (document.body) // other Explorers
	{
		x = document.body.clientWidth;
		y = document.body.clientHeight;
	}
	return [x,y];
}


// sets top margin of #container based on viewable area
function set_top_margin(pageheight){
	pageheight = pageheight * 1;
	innersize = GetInnerSize();
	h = innersize[1];
	m = 0;
	if(h>(pageheight+2)){
		m = Math.floor((h - pageheight) / 2);
		document.getElementById("container").style.marginTop = m + "px";
	}
}