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This site shows mobile version for desktop Opera

I'm using desktop Opera (version 11 alpha) and few days ago I've noticed that entire design of vanillaforums.org have changed. But when I checked other browsers, design is still the same. So I think that you have some errors in your methods of determinig Opera Mobile or Opera Mini (these can be determined by presence or string "Opera M" somewhere in the middle of UA string).
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I like this methodology better myself: http://detectmobilebrowsers.mobi/
Vanilla Forums COO [GitHub, Twitter, About.me]
We are doing a release later today, so this will be pushed to everyone.