//Open popup windows
function popup(address, popup_height, popup_width)
{
	var popup_left = (screen.availWidth / 2) - (popup_width / 2);
	var popup_top = (screen.availHeight / 2) - (popup_height / 1.7);
	var popup_dimensions = "height=" + popup_height + ",width=" + popup_width + ",left=" + popup_left + ",top=" + popup_top + ",scrollbars=0,resizable=0";
	var popup_window = window.open(address, "", popup_dimensions);
}