Below are SEO-related Add-ons for your Firefox browser—that can make your link building and search engine optimization  easier and simpler when searching, browsing and comparing.

SEO Blogger
SEO Blogger allows you to find the most sought-after keywords for your post without ever leaving your blog editing screen.

a4seo
An extension for the webmaster interested in SEO.

RankQuest SEO Toolbar
RankQuest SEO(Search Engine Optimization) Toolbar provides you quick access to more than 30 intuitive SEO tools. Alexa Rank and Page Rank provided by Alexa and Google respectively ensures the popularity of the site.

SEO Workers Analysis Tool
Allows web designers to perform a basic analysis of the page in your browser with a single click. The results from the SEO Workers Analysis Tool are structured into the following useful groups: General status, meta tags

SEO monitor
Information for SEO monitor users displayed in statusbar.

DeeperWeb – Boost and Customize Google Search
Easily navigate through Google search results using a fast, simple and useful Tag-Cloud technique. Use our Topic-Mapping-Technologies for quick access to answers, news, videos, blogs, Wikipedia and more.

Flagfox
Displays a country flag depicting the location of the current website’s server and provides quick access to detailed location and webserver information.

KGen
KGen (Keyword Generator) is an extension that allows you to see what keywords are strong on visited web pages. Than, you can retrieve them for social sharing (tag filling) or webmastering/SEO.

MetaTags
This sidebar displays page meta-information (metatags, links, etc.) Has automated search engine submission menu. Features include: Watches currently loaded Web page and automatically updates the sidebar. Displays metatags, links

SearchStatus
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.

Google Semantics
This tool helps interactive copywriters to get synonym for the keyword during your search on Google n which helps for better SEO using Google own Synonyms also referred as Latent Semantic Indexing (LSI) n is a vital element in Search Engine Optimization

Niche Watch Tool
SEO extension provides web developers and web designers the technical information required to beat your competitor websites in serps.It gives you backlinks number, indexed pages, keyword occurrences on the page, page rank, all in anchor,

(Advanced) SERPAnalytics Google search
SERPAnalytics is a new seo tool to analyze SERPs. This plugin allows you to search in Google and analyze the obtained results in SERPAnalytics.

SenSEO
SenSEO is an extension checking the most important on-page-SEO-criteria and calculating a grade of how good your site fulfills these criteria.

SeoQuake SEO extension
A Mozilla Firefox SEO extension aimed primarily at helping web masters who deal with search engine optimization(SEO) and internet promotion of web sites. Seoquake allows to obtain and investigate many important SEO parameters of

SEO Toolbar
Displays ILQ and other important SEO numbers.

SEOHAND
SEO services: Track sites placement at Google and Yahoo for any keyword. Watch Google PageRank (PR), Backlinks, Saturation over time. Graph and table presentation of the data.

DigMyLink
Reports the URL, Title, Description and Content of any link as you hover over it. Is supports any page you happen to be on. It does this by reading into the pages info without actually browsing to the actual page with little or no wait

Smart PageRank Toolbar
A small, simple, and powerful. It gives designers quick access to powerful SEO tools. It also includes the Alexa Rank and Page Rank (trademarks of Alexa and Google respectively).

SEO Link Analysis
Enriches the link data in Google Webmaster Tools & Yahoo! Site Explorer by showing the PageRank of the linking page, the anchor text user and whether the link is nofollowed or not.

Seostatus
This extension show Google PR and Yandex TYC in statusbar. Information can be load automaticaly or by click. Also highlight rel=nofollow and noindex tags. Numerating Google search results.

to.ly- URL shortener
URL shortening via to.ly service, one of the shortest URL services available. Shrink any long URL with a single click and use it in blogs, twitter or email. To.ly for Firefox is based on the service to.ly and uses SEO friendly redirects

Highlight My Site
Highlight your favorite sites in Google search results!

StomperTools
Featuring SNRanker, a visualization of Google, Yahoo, and MSN/Live for a specific query term using SVG. See how you rank! Useful for search engine optimization (SEO) assessment as well as exploring a topic.

Knofollo
Knofollo gives the web designer the ability to see “nofollow” attributes in hyperlinks. This is a simple tool with incredible possibilities for the webmaster. Knofollo effectively makes Firefox into a powerful Search Optimization Tool.

Fill Form
Web Directory Form Filler for Firefox – Submit to Directories in Seconds

SEOpen
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

SEO Toolbar
Displays ILQ and other important SEO numbers.

Foxy SEO Tool
Offers tools for search engine optimization (SEO), web traffic and page analysis for webmasters and web professionals.