SEO Tools and Firefox Add-ons:
Here are some Firefox Add-ons that I always use for Search Engine Optimization:
by Damian Smith
Provides some basic tools to help with search engine optimization. Including google backlinks, yahoo backlinks, PageRank check, http header viewer, and more. All features are available by right-clicking on an open area of a web page, or by using the included toolbar.
by Craig Raw
Display the Google PageRank, Alexa rank, Compete ranking and SEOmoz Linkscape mozRank anywhere in your browser, along with fast keyword density analyser, keyword/nofollow highlighting, backward/related links, Alexa info and more.
by M. Onyshchuk
InFormEnter adds a small, clickable icon next to every input field in a web form, from where you can select the item to be inserted – no typing required. You can configure it to display your frequently used information such as name, email, address and whatever else you want to be available from the form menu.
SEO for Firefox
See important competitive research and search engine marketing data directly inside Google and Yahoo search results.
Easily and automatically track your rankings (and rank changes) on Google.com, international versions of Google, Yahoo! Search, and the Microsoft Windows Live search engine. Free extension for the Firefox browser.
by Jan Dittmer
Show the IP address(es) of the current page in the status bar. It also allows querying custom information services by IP (right mouse button) and hostname (left mouse button), like whois, netcraft. Additionally you can copy the IP address to the clipboard.
by Chris Pederick
The Web Developer extension adds a menu and a toolbar with various web developer tools. It can help you easily errors on a certain web page for easy css or html editing.
by Kevin Freitas
Check the validity of links on any webpage. Check webpage links at a glance with simple color coding. Ditch those massive listings of bad links that provide no context and add LinkChecker to your arsenal of web development tools today.