In Conkeror, when visiting:

  http://www.newzbin.com

You'll notice the login table is rendered in quirks mode, to verify: 
  - open DOM inspector
  - inspect the "Account Login" box
  - inspect the "TABLE"
  - view it's CSS style rules
  - notice "resource://gre/res/quirk.css" is loaded/applied

If you perform the same task in Firefox, you'll notice that quirks mode is not applied. 

In case it's of importance, I am running:
   firefox 3.0.10
   xulrunner 1.9.0.10
   conkeror (compiled from 2009-04-24)