Web development using the newest technologies is obviously a newly emerged, and quickly developing, field. Fortunately, open-source toolsets promote developers and users of these technologies to build and release tools for these technologies.
Tools are our friends
The power lies within
about:config is a very powerful, and little used, configuration option for tweaking the underpinnings of Firefox.
via Born Geek:
The future is now...
For you extension developers, there is also a very exciting feature available in Firefox 1.5, Dynamic Development, which allows an extension to refer to a set of files locally on a disk without the need to repackage and reinstall the XPI during development. Changes are loaded each time, at runtime.