Opera, going fast towards version 10.00, detected severe problems with browser-detection scripts which interpreted “Opera/10.00” as Opera Version 1 and thus disabled a lot of features on some sites.
So they decided to change the string to “Opera/9.80” but put a “Version/10.00” at the end of the useragent string. So Piwik’s browser version detection needs something to recognize the new tag as the browser is identified as “Opera 9.80” although it should be “Opera 10”.
Read the whole explanation here: dev.opera.com .
Cheers,
-mARKUS