A simple but incredibly useful plug-in for Firefox. Colorzilla provides a small eye dropper in the status bar of your browser which can be used to determine the color of any DOM element. But it does more than this, it can also generate a palette based on your selection, allowing you to develop websites with matching colour palettes.
Another simple but essential plug-in. How many times have you found yourself wondering if a set of elements line up properly, or wondering just how far apart they are. MeasureIt allows you to draw a box on the your browser providing you with the exact dimensions in pixels. It couldn’t get much more simple than that.
The oldest and most heavily used tool hanging from my belt. I can’t even begin to detail all of the features this plug-in offers. Some examples include outlining table cells, resizing the browser’s view port, showing comments or hidden elements, validation tools, etc. Even after using this tool for many years I am still discovering new features, and I sometimes find myself wonder if they just recently added it or if it’s been there for years and I’ve never noticed it.
Far too often I see developers printing out their GET and POST variables using a print_r or similar method. Little do they know how much more simple they can make their lives by adding this handy plug-in to their arsenal. UrlParams not only allows you to view your GET and POST variables but it allows you to tweak them on the fly.
I’m sure all of you have your own personal favourites, there are many I considered listing but decided to limit it to my five most treasured plug-ins. If there are any you feel should be on this list, by all means please share them in the comments.