title: Why "Prevent this page from creating additional dialogs" appears in the alert box?
body: <p>In my Rails 3 application I do:</p>
  
  <pre><code>render :js =&gt; "alert(\"Error!\\nEmpty message sent.\");" if ...
  </code></pre>
  
  <p>Sometimes, below this error message (in the same alert box) I see: "Prevent this page from creating additional dialogs" and a checkbox.</p>
  
  <p>What does this mean ?</p>
  
  <p>Is that possible not to display this additional text and checkbox ?</p>
  
  <p>I use Firefox 4.</p>