The Mozilla Developer Centre is the starting point if you are interesed in doing any Mozilla based development. From developing extensions to working with the Firefox repository to making better websites, this site is full of great information!

Selenium is an automated web application testing utility that runs your tests directly in a web browser. Selenium uses JavaScript and Iframes to embed a test automation engine in your browser. The engine uses JavaScript that you can write by hand, but the makers of Selenium, have also created an IDE extension for Firefox that make writing your tests much easier. If you would like to try out Selenium and the Selenium IDE, you should check out this tutorial (complete with screencasts) that will get you up and running in no time at all!

Drag and Drop Upload is a very useful extension for Firefox that lets you drop files from Explorer or Finder onto a file upload box. W00t! No more clicking the browse button!

If you’re a blogger and use Firefox, you must download the CoLT extension from Born Geek. The extension adds three items to your contextual menu when you right-click on a link. You can choose to copy the link text, link location or even best the link text and location all wrapped up in a handy anchor tag! This has become my most used extension and has saved me much time!

Jonah Bishop from Born Geek has an excellent tutorial that will help you create a Firefox Toolbar Extension using nothing but a bit of JavaScript, XML, CSS and a Zip utility!

Validaty is a Firefox extenstion from Henrik Gemal that provides one-click HTML validation from your toolbar. If validation succeeds, the toolbar button turns green, if bad, it turns red and gives you the option to view the validation report.

I have created a 15 minute screencast that will show you how to Debug JavaScript with Firebug. I cover a number of concepts such as using the console, interactive debugger and timer features of the Firebug extension for Firefox. If you haven’t tried Firebug yet, I’m sure that this screencast will convince you to make it a part of your JavaScript coding workflow.

I hope you enjoy my first screencast! I plan on doing a few more over the next couple of weeks, so I would appreciate your feedback.

Launch the screencast now! (requires Flash)

If you’re writing AJAX code and/or standards-based web pages you should be using Joe Hewitt’s Firebug extension for Firefox. Version 0.4 has just been released and is the most significant upgrade to date. I have been beta testing this version for a couple of weeks now, and I can’t image developing without it. One of the greatest new features is a JavaScript Debugger that allows you to simply add breakpoints to your JS code, then step through your code line by line, and inspect local variables and the call stack. There are tonnes of other great features, so head over to Joe’s site and give Firebug a try!

Well now that Mozilla has officially released the Firefox 2.0 (bon echo) Alpha, you can now also get the Portable Firefox 2 Alpha 1.  All you have to do is download the Portable Firefox 2.0 Alpha 1 then run the file PortableFirefox.exe.  The profile is kept with the PortableFirefox folder so you don’t have to worry about messing up your other profile and the uninstallation process is simple…just delete the folder!  A nice way to test the latest and greatest Firefox!

It looks like Firefox 2.0 Alpha is beginning to make its rounds. This version of Firefox is a very early release meant for testing, so you should be well aware that the browser may be prone to crashing and will not include a full set of the features promised for the final release.
UPDATE: It looks like somebody jumped the gun on announcing this release.