It started After an update to Firefox 46 with my.yahoo.com losing all personalizations and Yahoo Mail appearing as in the attached image. After updating to 47, the problem remained. I removed all cookies associated with Yahoo and restarted the browser. my.yahoo.com now displays correctly, but Yahoo Mail and all other Yahoo based pages appear as the attached. I removed all add-ons and extensions, and replaced them one at a time, nothing works. This displays correctly in Opera, IE and Maxthon browsers.