//centered popup, specified width and height
function centerwindow(xw, yw, url)
{
	if (document.all)
	    var xMax = screen.width, yMax = screen.height;
	else
	    if (document.layers)
	        var xMax = window.outerWidth, yMax = window.outerHeight;
	    else
	        var xMax = 640, yMax=480;
	
	var xOffset = (xMax - xw)/2, yOffset = (yMax - yw)/2;
	
	return window.open(url,'livedemo','width='+xw+',height='+(yw-30)+',screenX='+xOffset+',screenY='+yOffset+',top='+yOffset+',left='+xOffset+',scrollbars=1,menubar,resizable');
}