title: Firefox not starting onreadystatechange function
body: <p>I made some javascript code for my website, it works without problem on opera and chrome, but not on firefox. </p>
  
  <p>Here is script:</p>
  
  <pre><code>function checkstate(who,row,cell)   {
      var zwrot="";
      var mouseEvent='onmouseover="javascript:bubelon(this.id);" onmouseout="bubeloff();"';
      var cellid="";
  
      ajax=new XMLHttpRequest();
      ajax.onreadystatechange=function(aEvt) {
          if (ajax.readyState===4 &amp;&amp; ajax.status===200) {
              alert("im here!");
              }
      };
  
      ajax.open('GET',"oth/work_prac_stan.php?usr="+who,false);
      ajax.send();
  }
  
  function sprawdzstan() {
      var lol="";
      var table = document.getElementById("usery");
      var re = /^&lt;a\shref\=/g;
  
      for (var i = 1, row; row = table.rows[i]; i ++) {
          if (row.cells[0].innerHTML.match(re)) {
              checkstate(row.cells[1].innerHTML,row,2);
          } else {
              checkstate(row.cells[0].innerHTML,row,1);
          }
      }
  }
  </code></pre>
  
  <p>The problem is, that firefox is not running function assigned to onreadystatechange. I checked in firebug, that response from php file is correct. </p>
  
  <p>Where is the problem? It works on chrome and opera, firefox just dont, no error in console, nothing.</p>