after update opera many times log out me from my account. WHY?
Please read this. There is no way people can try to help you if you don't provide information.
Also this topic subject is unrelated your issue.
If you look at the Oct and Nov stats for both WinXP and Win8.1, they clearly fall outside their otherwise trendlines, and seem to revert to trend in Dec 2014. Since in the rest of the almost-year's coverage, that kind of ripple is unique, I wouldn't put too much stock in what occurred there as being indicative of anything other than an aberration caused by pre-Holiday new computer sales. In other words, XP continues its steady decline from the 20's of % into the upper teens, while Win 8.1 continues its glacially-slow increase from the low single-digits to just under 10%. Win 7, has probably reached and sits at its all-time peak. The wild card yet to come, of course, will be Win10 impact when it finally emerges and in whatever final form.