[CentOS] Centos in the Browser string ?

I know Centos is a 100% rebuilt of whatever Red Hat has produced, even
though the version numbers are no longer visually identical and, as
Johnny always writes, "If it ain't in the Red Hat version, it ain't in
Centos" or words having the same meaning.

Having got circa 20,000 hits, from all round the world, to a single dull
web page in 2 days, I thought I would analyse the visitors' operating
system preferences.

I can isolate from the browsers string:-

Android
Darwin
iPad
iPhone
Macintosh
Windows
X11


My C5 Firefox string is "Mozilla/5.0 (X11; Linux x86_64; rv:38.0)
Gecko/20100101 Firefox/38.0".

Ubunto has "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:45.0)
Gecko/20100101 Firefox/45.0"

My questions are:-

(1) Why can't we have 'Centos' in the Firefox browser string ?

(2) Is 'X11' genuinely indicative of all 'real' Linux - both free and
commercial ?   Android also calls itself Linux.


Thank you.






-- 
Regards,

Paul.
England, EU.      England's place is in the European Union.