title: XMLHttpRequest open() returning access denied
body: <p>I have problem with xhr open() method. My code follows :</p>
  
  <pre><code>var xmlhttp=false;
  
  if(!xmlhttp)
      try
      { 
          xmlhttp=new XMLHttpRequest(); 
      }
      catch(e)
      {
          xmlhttp=false;
      }
  
  function returnPage(url)
  {
      if(!xmlhttp)
          return alert("Your browser doesn't seem to support XMLHttpRequests.");
  
      xmlhttp.open("GET",url,true);
      xmlhttp.onreadystatechange=function()
      {
          if(xmlhttp.readyState!=4) return;
          if(!xmlhttp.status||xmlhttp.status==200)
              alert(xmlhttp.responseText);
          else
              alert("Request failed!");
      }; //onreadystatechange
  
      xmlhttp.send(null);
  }
  </code></pre>
  
  <p>Call :</p>
  
  <pre><code>&lt;a href='#' onclick="returnPage('http://www.something.com'); return false;"&gt;Link 1&lt;/a&gt;&lt;/p&gt;
  </code></pre>
  
  <p>I'm using IE8 (because I'm building web slice) and I received error "Access denied". I found on the Internet that problem is that XHR isn't working across different domains, but I used code from Firefox Add-on which is working OK. And that add-on and "my" code (which are the same) are calling the same page. How that add-on have access and my code not?</p>