I went to the link you posted, proceeded to download, end user license agreement, accept and install, but got this message:
Software Installation
Install add-ons only from authors whom you trust.
Malicious software can damage your computer or violate your privacy.
You have asked to install the following item:
WebVisum (Author not verified)
https://addons.mozilla.org/firefox/downloads/file/127710/webvisum-0.9-fx.xpi?src=
Install Now Cancel
Before that message there was a popup saying "install 4 button unavailable".
When I hit the install button, I was prompted to restart Firefox, after which I was returned to the license agreement page, and I heard no indication that Webvisum had installed, or that I was logged in to Webvisum.
I received a long thread from the JFW users group about the Webvisum website no longer working and exploring alternative CAPTCHA solving methods. I want to pass along a suggestion someone gave about opening a file called Hosts. to get Webvisum to work. When I tried that I got no luck.
Thanks again for your feedback.

Douglas Richard Dexheimer
Chief of Braille Productions
Born-Again Productions
The Friedman Place, Apt.308
5527 N. Maplewood Ave.
Chicago, IL 60625
773-901-7306
cell 913-244-0612
drichardd@...
----- Original Message -----
From: "Sharyn Sobel" <sharynsobel@...>
To: "'Douglas Richard Dexheimer'" <drichardd@...>
Sent: Tuesday, March 20, 2012 9:02 PM
Subject: Webvisum

Doug,

I have researched and researched this issue to no avail.

I only found the Firefox website to download Webvisum v0.9 from.
https://addons.mozilla.org/en-US/firefox/addon/webvisum/?src=search
There are no comments on how it has worked out for people as there are zero
reviews. It says it works with Works with Firefox 3.0 - 5.* This version
came out July 30, 2011.

I have no other solution nor have I found any substitute product or plug in
for it.

Sharyn