My three Firefox plugins of choice that save me a lot of time troubleshooting and working out web development issues are:
1. Web Developer Extension: this one is a must have!
2. User Agent Switcher: I use this one occasionally to switch my UA into a crawler such as the GoogleBot since there are some cases where I modify pages to behave in a more search engine friendly manner if the user agent is a known crawler.
3. Live HTTP headers: This is my favorite tool for diagnosing pages getting cached that shouldn’t be cached and other general HTTP header work. The web developer toolbar also does this, but I like this one more since it’s real-time.
I asked my old coworker Dave at Urbanasoft what he was using these days and he pointed me to the following which look good as well:
1. View Formatted Source: for debugging missing closing tags, understanding which CSS settings are being applied to a certain tag, etc…
2. ColorZilla: a color picker, eyedropper, and page zooming tool.
What are your favorite Firefox web developer extensions?