Well, that's what you used to do when you got the "OMG, don't recognise your browser!!" from some site. I haven't needed to see whether it's different now because I haven't had that happen.
If you get site that wants "something else" you just have to change one line in the settings and it'll say it's that "something else" instead of opera. It's not a huge drama - but I've had no recent "raspberries" from any site I've visited.
I haven't had anything tell me that the browser wasn't "allowed" since I've been using it since Firefox chucked a complete wobbly and I couldn't be bothered trying to figure out why.
How did setting video "click to play" affect things? That completely solved my issue (which, BTW, was not this site but another which has only just introduced video ads on its site which slowed everything to an effective halt)
hmmm, if it was an issue with the ad server, you'd think more would have the same problem.
(I looked up my log, I disabled my automatic video player because of video ads on a different site - BUT that also slowed my browser to a crawl. I've been a happy camper since I turned it off)
Not sure whether this is your version (I don't use chrome), but if you change your settings for flash content to "click to play" videos won't run until you click on them. If it's not where this article says, have a scout around...