If you visit many webpages that require you to login everytime, if you are no speed-typist and your email is very long, or if you simply don’t want to type it anytime, this add-on is what you are looking for today. Paste Email is a Firefox add-on that memorizes up to 16 email addresses, and it lets you paste any of them into any login box with a single click.

IE Tab is a web development add-on, which gives you the possibility of having Internet Explorer’s rendering engine integrated into your Firefox session: on any open tab, you can simply click a button, and it’ll be automatically reloaded using IE’s engine, as if you were using Microsoft’s own browser instead of Firefox.

Sometimes web pages get cluttered and you want to read a specific part - JusThis lets you focus on that part by removing the rest. Highlight just a few words from the area you're interested in, select "JusThis" from the right-click menu and voila!

HYPER-ANCHOR is the next generation of bookmark. You can make HYPER-ANCHOR for any element of a webpage (sentence, image, table, etc...), and put it into the old bookmark menu. When you use HYPER-ANCHOR from the menu, you can easily return to the element. This means that you don't need to search the position of the element in the web page, but the HYPER-ANCHOR leads you to the position by scrolling and informs of the element by using your own choice of customized indication method.

Update: SEO for Firefox should work on any international version of Google or Yahoo! now.
Why Do Over 50,000 Webmasters Use SEO for Firefox?

Want to know why Google or Yahoo! ranks pages? If so this is the Firefox extension for you. SEO for Firefox pulls in many useful marketing data points to make it easy get a holistic view of the competitive landscape of a market directly in the search results.

Want to learn more? Watch this video and/or read on.