With Firefox (Build identifier: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.3) Gecko/20100402 Namoroka/3.6.3), I also got this warning.

Detecting the browser instead of the features is often bad practice: http://www.jibbering.com/faq/faq_notes/not_browser_detect.ht...

I will add that to my whitelist. You should be able to close the warning and continue.

I'm whitelisting OS/Browser combos, and I haven't added linux yet.

I'm using Chromium 4.0.299.0 (36335) on my Mac and I get that popup too.

According to jeresig, author of jQuery, one should not perform browser detection, instead you should use feature detection. Browser agent is not going to give you an accurate picture of what is supported because every browser likes to say they are mozilla/webkit/netscape/etc.

Also add Namoroka and Minefield, test versions of Firefox. Instead of whitelisting, can't you run some test code client-side and only prompt when you're sure the browser doesn't support it?

Using Firefox 3.5.7 on Ubuntu (Karmic) and got the same popup.