webtools.debug connects Eclipse to Firebug, the web page debugger running inside of Firefox.
This web page is used to illustrate the features. If you have webtools.debug installed you can open Firebug and try it
webtools.debug launches Firefox when you select Run on Server from the Eclipse Editor Context Menu,

As you visit resources in Firebug,

webtools.debug keeps your editor in sync with the corresponding file in your workspace:

Control the synchronization of Firebug and the editor using the double arrow button at the bottom of Firefox in the status bar

webtools.debug routes error messages from Firefox's Javascript Console to Eclipse's Problems view

webtools.debug has two kinds of configuration:
The Run On Server feature relies on you to select Firefox with Firebug as your preferred Web browser. For most users,
installation of webtools.debug will create a new web browser configuration entitled Firefox with Firebug.
You can verify and select this browser from Window -> Preferences -> General -> Web Browser. The values for
the configuration can be changed by selected the configuration and Edit. For webtools.debug to succeed, the
Parameters field must be "(internal configuration, do not edit)". The location field can be changed, either to
accommodate an unusual installation of Firefox or to use a different Firefox version.

The following information is provided to help users diagnose unusual issues or try unusal configuration. Future versions of webtools.debug may adopt different approaches to these issues
Firebug is installed in the .metadata/.plugins/com.ibm.etools.webtools.debug/Firefox directory
for the workspace and Firefox is run with command line
parameters that cause it to use this directory and a parameter that
allows multiple copies of Firefox to run with different configuration values.
The first use of webtools.debug builds this configuratoin directory and installs Firebug.
Subsequently the Firefox "profile" or configuration will depend upon the workspace.
You may add other Firefox extensions, store bookmarks, and so on as you would normally do with Firefox, but all of these values
are stored in the workspace, not in your desktop Firefox configuration nor in other workspaces you may open later.
For each project you can select whether or not webtools.debug should reload pages when you build your project or save files in the editor. These selections are done from the Web Debug page of the Project Properties.

To learn more about the features and their use, try the tutorial.