function popup (file) {
var window_width = screen.availWidth;
var window_height = screen.availHeight;

   var url = file;

if (document.all) {
   var newwin = window.open("","","left=0,top=0,width=500,height=400,scrollbars=yes,fullscreen=no");
   newwin.location = url;
} else {
   window.open(url,'new_win','width=500,height=400,menubar=no,status=no,location=no,fullscreen=no,directories=no,resizable=yes');
   }
}