I recently installed the plugin Simple History, and was alerted today that in Chrome my site was showing only the mobile version, even on normal computer. I deactivated the last plugin I installed, which was to install the aforementioned Simple History, and voila! Chrome displays the proper theme for desktop browsing. Firefox and Safari showed the appropriate theme the whole time, not sure on IE. Not sure where the issue lies, but I thought you should be alerted to the problem. I have posted about this over in Simple History's support area as well.