I'm trying to get FireBug Lite working with IE7. Given this code (and nothing else):
<link rel="stylesheet" href="../../css/third-party/jquery.ui.all.css">
This is a test!
This is a known bug that affects IE7 (and IE8) and is being tracked on the firebug issue tracker.
This is still an issue on all channels (Firebug 1.4 stable/debug/beta/developer).
Disclaimer: If you're going to use these methods, please subscribe to the discussion about this bug and make sure you stop using this contrived one either when it's fixed, or Firebug 1.5 comes out.
If you need to use firebug now, you could use firebug 1.3. This method I can't find documented anywhere...
A better approach would be to use Firebug 1.3 as a bookmarklet. I've hacked up this bookmarklet URL based on the firebug release archive:
Just dump it into your 'links' bar using the above in the URL field.