Page Speed, the popular Firebug/Chrome add-on -by Google- for evaluating the performance of web pages now gets an online version.
It offers a very similar functionality with the Firebug version, analyzes the page performance and comes with suggestions that are categorized in priorities to improve it.
This free service also has a new feature: "suggestions for the mobile version of a web page" which are tuned for the unique characteristics of mobile devices.
FireQuery is a Firefox add-on that extends Firebug with new jQuery-focused features.
It adds extra functions to the HTML tab like showing embedded data elements & event handlers inserted using jQuery.
All the jQuery expressions are presented in Firebug Console + DOM inspector and elements in jQuery collections are highlighted on hover.
Also, the jQueryify bookmarklet is integrated into FireQuery which makes injecting jQuery into any website possible.
NitobiBug is a browser-based, cross-browser JavaScript object logger script.
Using this debugger, you can inspect a JavaScript object to discover its members and the values of those members.
NitobiBug intelligently discerns simple types like strings, booleans, and numbers, from complex objects like error messages and objects.
var myDomObject = document.getElementById('someID');
nitobi.Debug.log(myDomObject);
is enough. It will present you the results in a pop-up like draggable, expandable interface.
As there are nice tools for debugging like Firebug but few are cross browser, NitobiBug works on the following browsers:
