Do you remember Jetpack?
It is the Mozilla Labs project that makes the add-on building process easier, mixing elements of HTML, CSS and JavaScript.  Mozilla has released an awesome Jetpack Gallery, which serves as a community for Jetpack developers and add-on users.

One thing is for sure, with the correctly equipped Firefox browser, you too can become a better web designer or developer. How so? Well, Firefox has some really great tools for both of these jobs. Finding the one that doe the best job, is another job all on it’s own.
Firefox has a lot of web development add-ons you can use, however these are the best of the best at what they do.

Console² – Console² (pronounced Console Squared [...]

Ever wanted to write your own Firefox extension, but thought the process was too drawn out or difficult to do?  Jetpack is looking to use open Web technologies to enhance the browser.  The idea here is that if you can make a web page, you will be able to build an add-on for Firefox.
This video does a great job at giving you a basic walk-though of what Jetpack development looks like thus far:

Mozilla Labs Jetpack – Intro & Tutorial from [...]

Thanks to Firefox and some of the great add-ons that have been developed for it, your browser is your best friend when it comes to web site design.  From CSS tools, to promoting your domain, here are 10 of the most popular web designer tools for Firefox.
Any of these add-ons would be great to add to your own proverbial web designer’s toolbelt.

ColorZilla – This advanced eyedropper and color picker will help you find out exactly what color is being used [...]

Can you believe that is Google Reader?  Nah, me neither.  There has to be some sort of oddball voodoo magic going on here, right?  What?  You say it is a Greasemonkey script?  Helvetireader breaks Google Reader down to just the things you need.  I true, “Woah, that is awesome” fashion – the userscript creator also encourages people to customize the CSS and make it their own.  (found via Lifehacker)

When web development and design is mentioned, everybody’s top Firefox extension is the Web Developer toolbar. There are a few other choices out there for design and coding tools that you might have not of seen before.
View Source Chart – This extension does one job and does it well. It draws colored boxes around different source codes to help you read the information better. Instead of black and white confusing stuff – it’s all colored man. [...]

Finding yourself in a bind with your web site design? Maybe you just can’t get your CSS to level out with your HTML? If you find yourself in these shoes we talk about, you might need to pick up the Total Validator extension for Firefox.
Perform multiple validations and take screen shots in one go. This 5-in-1 validator works with external, internal, or local web pages using the Total Validator service or local copy of the Pro desktop [...]

Need a quick and painless way to view javascript in Firefox? Check out JSView!
Well now there’s a much easier way. You can use the JSView extension to solve the problem. You can access it from the context menu, from the toolbar, from the view menu, or from the status bar. If the website you are viewing contains any external js/css files, an icon will appear that says “CSS”, “JS”, or both. Each individual file can then be viewed by [...]

Ever felt the need to get rid of Google’s boring white background? Well I have run across three really neat styles that somebody has created for Google via the Stylish Firefox extension. To use these, you will have to have Stylish installed.
+ Find Out How You Too Can Make Google Beautiful!

When you mix a little CSS code with Firefox, you get a neat trick that no other browser out there can do. Well, even if they could I wouldn’t care because this is called Firefox Facts, not IE Facts! Anyways, check it out – learn how to do it yourself and be careful where you middle click!
+ Check Out This Funny Firefox Bug Test!