This is by far the most used firefox extension I have. With a simple mouse click, I can evaluate a websites PR, its alexa rating, backlinks, Y! Links, edu links and see if it is dmoz listed. Although there are lots of SEO tools available, this one wins hands-down for its ease and simplicity. You can find the plugin here.

Once installed you’ll find the SEO icon above installed on the bottom right of your firefox browser. Click to activate the plugin, then on any webpage your browsing, right-click, select ‘Seo for Firefox’, then ‘Lookup this page’ to get a quick look at all the seo information for that page like the capture on the left. the figures here are an evaluation of google.

The two most important values are Page rank. These range from 0-10. Anything 3+ is respectable, but too much emphasis is placed on page rank these days. Some sites may have little or no traffic, but still receive a high PR.

A better metric on SEO for firefox is alexa.  This measures the traffic on the site you are evaluating. The lower the value, the better traffic going through that site e.g. Facebook has an alexia rank of 5, but the scale can rise to millions. So if your site has an alexa rank of 90,000, then your site is <!– /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:”"; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:”Times New Roman”; mso-fareast-font-family:”Times New Roman”;} span.EmailStyle15 {mso-style-type:personal; mso-style-noshow:yes; mso-ansi-font-size:10.0pt; mso-bidi-font-size:10.0pt; font-family:Arial; mso-ascii-font-family:Arial; mso-hansi-font-family:Arial; mso-bidi-font-family:Arial; color:windowtext;} @page Section1 {size:595.3pt 841.9pt; margin:72.0pt 90.0pt 72.0pt 90.0pt; mso-header-margin:35.4pt; mso-footer-margin:35.4pt; mso-paper-source:0;} div.Section1 {page:Section1;} –>

effectively the 90,000th best site on the net!