Troubleshooting "document URL is undefined" error message in Yahoo Mail
<p>Whenever I access a message at Yahoo Mail, a little window appears over the site:</p>

<blockquote>
  <p>Java Script</p>
  
  <p>Error: document URL is undefined</p>
</blockquote>

<p>My computer works with XP SP3, Firefox Browser. Avast and Spy-bot, all software fully-updated.</p>
