Here is what you should do
I’ve just spent the last 25 minutes trying to figure out how to show no-follow tags using a Firefox add-in. I knew that the add-in existed but what was the name of it?

My hunt let me to Mozilla’s official add-in page. I searched for “nofollow” and found the SearchStatus add-in by Craig Raw. The version listed is 1.20 and for some reason (the reason might be me) I just couldn’t get this add-in to work.

After finding this page which contained the newest version 1.21 of SearchStatus everything worked out. So here is a quick guide if you don’t know how to add the add-in into Firefox.

Step by Step
1. Download the xpi file here

2. Open Firefox > File (menu) > Open File > “the xpi file”

3. Click Install Now
 

4. After restarting Firefox you will see this
 

5. Right clicking on the little logo will enable you to choose “Highlight Nofollow Links”
 
This toolbar will provide you with tons of other features but this guide was only meant to show you how to see no-follow links like these: