Opening webpages, posting to Google+, replying on Twitter, reading Wikipedia articles, watching Youtube clips, etc, are action conducted via Firefox, Ubuntu's default web-browser, that constantly sees new releases, due to its recently adopted rapid release cycle.
Being part of a rapid release cycle, Firefox is, as seen in the latest months, expressed via both UI changes-related and new features-based releases, versions constantly bringing changes and pushing Firefox forward on multiple levels (UI, solid development tool, etc).