function mypopup(url,popup_width,popup_height)
{
    //var popup_width  = 500;
    //var popup_height = 450;

    mywindow = window.open (url,"_image","width="+popup_width+",height="+popup_height+",toolbar=no,scrollbars=yes,resizable");
    mywindow.moveTo((screen.width-popup_width)/2,200);
}