function popup(file,imgwid,imghgt){
var winl = (screen.width - imgwid) / 2;
var wint = (screen.height - imghgt) / 2;
window.open(file,'popup','width=' + imgwid + ',height=' + imghgt + ',resizable=1,scrollbars=1,top=' + wint + ',left=' + winl + ',toolbar=0,location=0,directories=0,status=0,menubar=0,copyhistory=0');
}