http://console2.mozdev.org/

Console² , is used not only for JavaScript errors, but for CSS errors as well. This extension takes this into account by providing a simple possibility to display errors by type. It let's you display errors filtered by type (Errors, Warnings, Messages), language (JavaScript, CSS, XML) and context (Chrome, Content). Furthermore it provides a simple search box (as seen in the History and Bookmarks sidebars) and some accessibility improvements.
  1. [2010/05/24] software development articles directory *2 by Jameswoo (1560)
  2. [2010/08/10] [Ebook] Firebug 1.5: Editing, Debugging, and Monitoring Web Pages by kuppa (5498)
  3. [2010/05/20] [Ebook] Beginning JavaScript, 3rd Edition *4 by rongcon200 (4190)
  4. [2011/07/19] TDD Javascript by PierreM (2350)
  5. [2012/09/12] JavaScript Patterns *1 by papputheking (1262)