I was working with the awesome theme Salient today and noticed that in FireFox and Internet Explorer that some of the icon short codes had stopped working. Strange enough they are all working in Chrome. I noticed that firebug was reporting the error: bad URI or cross-site access not allowed. Salient uses Font Awesome to generate icons and fonts.
After a quick Google search I was able to find a solution that solved my issue. Hope this can help someone else.
Add the following to your .htaccess
Header set Access-Control-Allow-Origin "*"
Happy WordPress Blogging!