So, as I told Dr. Drake in class, I'm going to make a post talking about a few of the web development tools that I like to use. There are a few different ones that I like to use for Firefox including Firebug, MeasureIt, and Colorzilla. An addon that I like to use that is unrelated to web development is Download Statusbar.
Firebug is an addon that allows you to inspect various elements by either hovering over it in the web page or by searching through your source code in firebug while it highlights each element as you hover over it.
MeasureIt is an addon that lets you measure the distance between two items in firefox, it gives you the distance in pixels which is very helpful when trying to set margins or measure the distance between two elements while developing a web page.
Colorzilla is one of my favorite addons. Think of the eyedropper in paint. It allows you to click the tool and click any color on a web page in firefox and it gives you the rgb numbers so that you can replicate it if you want when developing a page. It is especially helpful if you're trying to replicate the colors of a web page for whatever reason because then you don't have to go through the CSS to look through all of the colors.
Finally, while not helpful for development, it is a convenient little tool that I like because it keeps pop up windows out of my face when I'm trying to download things. Download Status bar is a must have for me personally.