What about IE6/IE7
According to our code base we should not be serving any Javascript to IE6/IE7 browsers other than the startup code that checks for browser compatibility. [..] However, we do see some user agents on bits for IE6/IE7. For example [IE6] is responsible of 1% of total pageviews.
Likely this browser is not identified by our code as IE6 and thus is being served Javascript (this is a bug) We need to do a little bit more research here to see the javascript requests being served.