Rated 5 out of 5 stars

Good add-on, but users of Firefox 2.1.x or higher should get Vitzo's WHOIS add-on instead: https://addons.mozilla.org/nl/firefox/addon/10494

Rated 5 out of 5 stars

I use it all the time. I was disappointed that it doesn't work with FF3.x

But that was an easy fix. Download the xpi file and open it in Winzip. Edit the file called install.rdf (I used notepad) and change the maximum version to read 3.2.0.*

Rated 5 out of 5 stars

Does exactly what I need: I can highlight a domain name on one site, right-click, choose domainFinder, and a new tab will open with the whois information of the domain I had highlighted. Saves me a lot of time in my business!