Hello Joanne.

I believe there are other uses reporting a similar problem. You may want to contact the toolbar's author for support. In the meantime, make sure you read this support article about that specific error:

https://support.mozilla.com/en-US/kb/Unexpected+installation+error+-203+when+installing+add-ons

I hope it helps, in any case.

while trying to install farmville tool bar firefox asks to install this plugin

http://ff.conduit-download.com/27/243/CT2438727/Downloads/Firefox/Releases/2.5.8.6/10-03-29-09.59.44.561/zynga.xpi

and after installing this firefox want me to restart it and after restarting fire fox it ask me to do it again and again and again i am tired doing this so plz give an solution for this