function centerWindow(page)
{
    x = (screen.width - 800) / 2;
    y = (screen.height - 600) / 2;
    if (x < 0) x = 0;
    if (y < 0) y = 0;

    args = "width=800,"
	+ "height=600,"
	+ "location=0,"
	+ "menubar=0,"
	+ "resizable=0,"
	+ "scrollbars=1,"
	+ "status=0,"
	+ "titlebar=0,"
	+ "toolbar=0,"
	+ "hotkeys=0,"
	+ "screenx=" + x + ","  //NN Only
	+ "screeny=" + y + ","  //NN Only
	+ "left=" + x + ","     //IE Only
	+ "top=" + y;           //IE Only

    window.open(page, 'popup', args);
}