Mozilla Firefox is a browser that provides a lot of Add-ons for its users, and you can find a lot of useful extensions for website developers. Below are a couple extensions explained to help you make the best use of Firefox.
One of the most important parts of developing a website is cross browser checking, for example making sure that the site looks the same in multiple browsers. Firefox provides an extension called user agent switcher, which can be customized with the user agents you need such as Internet Explorer and even mobile user agents. This extension can save you a lot of time when it comes to cross browser testing.
One feature that can save you a lot of time is called GA?, which checks the site to see if it has Google Analytics installed and displays either a color image in the bottom bar of the browser or an uncolored graph to show that it has no GA coding. You can use Firebug to check the GA coding currently on the page quickly, instead of having to view the page source.
A great extension for finding the color value in a part of an image or any part of a site is ColorZilla, this extension will display a little eyedropper on the bottom right bar of the browser and will give you the name of the color, RGB and hex value. This feature combined with Firebug can help you change the color styles of your site in real time without having to make changes to the live css file directly.
After making changes to a site in real time in your browser, you might want to save the look and feel of the new changes made. There is an extension called FireShot that can help you take an image of the whole page or just the part that shows on the browser. This can come in handy if you need to show it to a client or coworker and get their feedback, without actually making the changes to the live site.
Development of sites using Firefox can be a lot easier and faster when using the tools described above. This can help your site load time improve as well as design without having to make any changes to the live site; just making changes in your own browser.