Sorry but CentOS 5 is essentially outdated due to using packages that are from over years ago. The last version to perhaps work is Firefox 3.6.18 without doing dependency installs if possible like at http://warped.org/blog/2011/03/29/firefox4_redhat_5/ http://www.mozilla.com/en-US/firefox/all-older.html This is the downside of using a LTS Linux distro as they choose to stay with old stable packages versus being more up to date. http://www.mozilla.com/en-US/firefox/5.0/system-requirements/ http://www.mozilla.com/en-US/firefox/4.0/system-requirements/ Oh and Please do not comment in the bug 621704 bug mentioned in article as there is enough comment spam there already as bugzilla is not a forum or like a comment section of a blog.