// opens a popup window in the center of the screen
//
function OpenCenteredPopUp(sFile, sWindowName, iWidth, iHeight)
{
	var maxY = screen.availHeight;
	var maxX = screen.availWidth;
	var x = (maxX - iWidth) / 2;
	var y = (maxY - iHeight) / 2;
    var w = window.open(sFile, sWindowName, 'status=no,scrollbars=no,width='+iWidth+',height='+iHeight+',screenX='+x+',screenY='+y+',top='+y+',left='+x);
    if (w != null)
	    w.focus();

	return w;
}