User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-GB; rv:1.9.1) Gecko/20090624 Firefox/3.5 Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-GB; rv:1.9.1) Gecko/20090624 Firefox/3.5 Prism can not be installed from the add-ons menu for firefox 3.5, even ignoring the version check. Reproducible: Always Steps to Reproduce: 1. Using firefox 3.5 2. Go to the site https://addons.mozilla.org/en-US/firefox/addon/6665 3. try to install Actual Results: Prism for Firefox 1.0b1 could not be installed because it is not compatible with Firefox 3.5. Expected Results: It should have installed.