User Interface
Port of Firebug's Visual Object Representation (aka Reps) Recreation of Firebug 1.3 User Interface with pixel precision Menu options Resizable Side Panel Skinnable Interface
CSS
CSS cascading view CSS inheritance view Live editing CSS rules and properties Autocomplete as you type feature, with smart suggestions (you'll get only the suggestions you need for each property) Increment/decrement with UP/DOWN and PAGE UP/PAGE DOWN keys
Inspector
Full BoxModel Highlight including margin, border, padding and content boxes The BoxModel is highlighted when you move your mouse over a representation of a HTML element, in any of the place of the User Interface Elements are selected on-the-fly while using the Inspect tool
Console
console.group(), console.groupCollapsed() and console.groupEnd() console.trace() (now with file name and line numbers for some browsers) Command line API functions $(), $$(), and dir() Command line shortcuts $0 and $1 for recent selected elements Autocomplete (tab, shift+tab) can capture console messages before DOM document creation (when installed at the HTML header)
Core
XHR watcher (with Headers, Response, Post and Params tabs) Port of Firebug Library (aka Lib, FBL) Port of Firebug DOM Templates Engine (aka Domplate), the magic behind Reps Plugin system like Firebug Context-independent (will allow cross-iframe debugging, and persistent popups) Persistent popups Synchronization across different windows (iframe, popup)
And more...
For a complete list of changes, check the changelog.
1.3. What's Not in Lite?
Some features are not included in Firebug Lite 1.3, but due the new core that supports code sharing from Firebug, are likely to be included in the Firebug Lite 1.4 version:
Live editing for all panels Layout Side Panel Context menu options Tooltips (to show colors and images) Search feature
Other features though are too dependent in browser internals and will not be supported (at least in a near future*), such as:
Javascript debugger / Javascript profiler Net panel / HTTP and XHR monitor Access to restricted URI resources Highlight HTML changes
*Discussions about remote debugging indicates that should be possible to support JavaScript debugging in browsers like Google Chrome and Opera in the future.