// Opens a centered popup window giving it focus
function OpenCenteredPopup( sURL, sWindowName, nWidth, nHeight ) 
{
	window.open( sURL, sWindowName, "width=" + nWidth + ",height=" + nHeight + ",top=" + ( ( screen.height / 2 ) - ( nHeight / 2 ) ) + ",left=" + ( ( screen.width / 2 ) - ( nWidth / 2 ) ) ).focus();
}