function getWindowHeight()
{
	var myHeight = 0;
	if (typeof(window.innerHeight) == 'number')
	{
		//Non-IE
		myHeight = window.innerHeight;
	}
	else
	{
		if (document.documentElement && document.documentElement.clientHeight)
		{
			//IE 6+ in 'standards compliant mode'
			myHeight = document.documentElement.clientHeight;
		}
		else
		{
			if (document.body && document.body.clientHeight)
			{
				//IE 4 compatible
				myHeight = document.body.clientHeight;
			}
		}
	}
	var top;
	if (myHeight<674)
	{
		top = 0;
	}
	else
	{
		top = Math.round((myHeight-674)/2);
	}
	document.getElementById('canvas').style.top = top.toString() + 'px';
	document.getElementById('canvas').style.display = 'block';
}

window.onresize = getWindowHeight;