651
Firefox is on the brink of being dropped by the US Government
(www.brycewray.com)
This is a most excellent place for technology news and articles.
They are talking about .gov websites. Any website operated by the US government should, at least according to their own standards, develop for and test for users using Firefox. If this is followed in practice the article doesn't really cover.
It's USWDS, firefox should still work as long as it is standards compliant.