I am running Ubuntu 14.04 LTS 64-bit and the version of Firefox that comes with this version of Ubuntu. I recently went to a website and got a notification that my version of Firefox was no longer supported. I was not aware that Firefox was not being updated as I update regularly. I tried updating from the command line as well as using the Ubuntu Software Updater but neither of these work and my Firefox version is still stuck. I have researched online and have tried adding the Firefox security PPA as well and installed that but when I launch Firefox it is still the same old version that opens.
I eventually tracked down the issue to a plugin I had installed a while back that allows you to modify the header information to look like your using a different OS and browser so the sites I visited were thinking I was on Windows and using an older version of Firefox.
Firefox 38 is the latest version. I'm pretty sure, if it's a ribbon at the top, or a box in the site, that is an ad. Ignore it.