What do you mean upgrade?
You're viewing a single thread.
I'm going to guess it's because they wanted to account for older windows operating systems and they made that everything that isn't like windows 7+ mac and stuff it pops this message and the linux string is probably taken by the useragent.
sorry for bad English
English is all good, and honestly that's a good point. I tend to forget that the browser is what forwards the OS to the website, not the OS itself