title: Best way to locate source of Warning: Empty string passed to getElementById()
body: <blockquote>
    <p>Warning: Empty string passed to getElementById().<br>
    Source File: chrome://browser/content/browser.xul<br>
    Line: 0</p>
  </blockquote>
  
  <p>Some days ago I started getting the above message while developing my site. Things are working as they should (or at least I think they are), but I want to find out where this is coming from. I use jQuery so do not use <code>getElementById()</code> directly. Plus I have Firebug and the Web Developer extension for Firefox running.</p>
  
  <p>I could laboriously put in code to check for an empty string being given to a jQuery selection or maybe look into jQuery itself, but my skills are minimal, so I'm asking here if anyone has offhand a good idea for quickly locating the source of the warning messages.</p>