Firebug
If you spend time building web pages, working with CSS, Ajax, javascript etc this plugin can be amazingly helpful. It allows you to inspect DOM elements on the page, see what css styles they have applied to them, where these CSS styles are defined and even preview changes without having to modify the source.
HttpFox
HttpFox allows monitoring of http traffic between your browser and the web server. Also allows you to inspect headers, POST data, cookies etc. Incredibly useful when working with Flash applications when you want to see what data is being loaded in, and also for easily checking for missing or broken page components.
YSlow
Another tool for website optimisation. Developed by Yahoo, YSlow analyses various components of a web page and gives you tips on areas that can be improved based on Yahoo’s rules for high performance web sites. It also includes neat tools to do things like image optimisation. YSlow runs on top of Firebug and so you’ll need to have that installed before you’re able to use it. Yahoo’s Best Practises for Speeding Up your Website are a real goldmine of information and well worth looking into if you’re involved with making sure your getting the best possible performance from your website.
HTML Validator
The benefits of having correct, cleanup HTML/XHTML markup are obvious. This extension parses and validates your markup using two tools from the W3C – Tidy and OpenSP. You are then presented with a list of issues, making fixing poor markup a quick and easy process. It also has a useful feature that allows you to view html source after javascript execution, which is useful when working with Ajax.
Web Developer
The web develper extension brings together stacks of different tools that are useful for web development, tools for inspecting web pages, validating, disabling components, resizing the browser window, etc etc.
Flash Tracer
Very useful if you work with Flash, this extension allows viewing of trace statements from a Flash movie when it is embedded in a web page. Requires you to use a debug Flash Player.
Flash Switcher
I use this in conjunction with Flash Tracer. As the debug flash players can be slow compared to the normal player, you ideally don’t want to be running it all the time. Flash Switcher gives you a quick and easy way to switch between different flash versions. It also allows you to test your flash under different flash player versions.
FireShot
This extension doesn’t feel quite as slick as other extensions but provides some neat functionality. It gives you a quick and easy way to take a screengrab of the current page (either visible area or the entire page), and then carry out simple edits and make annotations to the grab before saving it off or sending it via email. Very useful when you want to send someone a screengrab highlighting an issue or area of interest.
ShowIP
A simple extension that tells you the IP address of the site you are visiting. If you maintain several servers this can be useful to tell you where a page is hosted
Clear Cache Button
Allows clearing of your web cache without having to delve through submenus. if you find yourself doing this a lot, this extension is worth getting.
