var url, timer;
var img = new Image();
var sub;
var count;

function screenshot(_url) {
  if (_url == '') return;
  url = _url;
  sub = document.getElementsByName("sub")[0];
  if (sub) sub.disabled = true;
  img.onload = check;
  img.src = url;
  count = 100;
}
function refresh() {
  if (--count) img.src = url + "?rnd=" + Math.random();
  else img.src = url = 'http://screenshot.com.ua/failed.gif';
}
function check() {
  if (this.width > 1 && this.height > 1)  {
    clearTimeout(timer);
    show();
  }
  else timer = setTimeout("refresh()", 1000);
}
function show() {
  var ss = document.getElementById('screenshot');
  if (ss) {
    ss.onload = function() { if (count) this.className = "thumb"; };
    ss.src = img.src;
  }
  else alert("Ooops...");
  if (sub) sub.disabled = false;
}