function open_popup(l,h,url) {
height_sc=Math.round((screen.availHeight-h)/2);
width_sc=Math.round((screen.availWidth-l)/2);
window.open(url, "page", "toolbar=0,location=0,directories=0,status=0, scrollbars=1,resizable=1,menubar=0,top="+height_sc+",left="+width_sc+",width="+l+",height="+h);
}