Although Chrome seems to be winning the browser wars these days, I still like to develop against Firefox first and then tweak/hack CSS for compatibility with other browsers afterwards. I do this because I believe that Firefox most closely adheres to the HTML and CSS standards when it renders sites. I’m pretty sure that this belief used to be true, but I’m not certain if it’s technically correct today. However, as an approach it still seems to work pretty well. I’d be interested to hear your views on this.
I thus know more about Firefox add-ons than add-ons for other browsers. Here is my list of essential Firefox add-ons, which I’ll keep up-to-date:
Not really a developer tool, but a great tool for recording and replaying macros in Firefox. I tend to use it to log in to sites that have laborious access procedures or have auto-complete disabled.
Another one from Chris Pederick, and very useful for testing out different user agents with your code. When used in conjunction with the re-size feature in the Web Developer toolbar mentioned above, you can get your sites in a pretty good state to work on mobile devices, before testing on the devices themselves.
Useful when working with SAML based single-sign on solutions, which I’ve been doing lately with ADFS.
That’s all for now folks!