Well, if some people (and I'm one of them) prefer the old Firefox look of squared tabs, the add-on bar (which will be removed in version 29) the old download window, hide the tab bar with one tab open, etc, etc; they can have it with a new linux browser called Pale Moon and these things don't need an add-on to replace what the FF developers have taken out of FF. They're in there by default. It made it's public release in January about 7 weeks ago. I use linux Pale Moon. The same add-ons which work in Firefox work in Pale Moon too. And you should also be able to view a YouTube video and hear the audio without doing anything extra since I can.
Pale Moon used to be for Windows only, but with the advent of Mozilla going with the the Australis UI change and making it very similar in look and feel to Chrome, some of us on the Pale Moon forum asked the developer of Pale Moon if he would make a linux version of Pale Moon since the Windows only developer of Pale Moon said he will not go with the Australis UI change. He said he didn't have the time since Windows only Pale Moon "fills enough of his plate".
However, he said if any user on the forum wanted to try and make a linux version of Pale Moon, he would help them do so. Someone took him up on his offer starting in August of 2013. If anyone would like to try linux Pale Moon which looks like the old Firefox, it can be downloaded at SourceForge. BTW, both the developers of Windows only Pale Moon and linux Pale Moon said they will NOT switch to the Australis UI change which Mozilla is going with for Firefox. http://sourceforge.net/projects/pm4linux/files/24.4.0/
Very important. Once on the page, look for and left click on the blue colored word "Home" and it will take you to another page where the newest tarball version is (24.4.1). Left click on newest version and it will take you to another page where you pick version 24.4.1 in either 32 or 64 bit. You can try it out "without" installing it since it has the executable file in it.
Download the tarball, extract the palemoon folder from the tarball to where you want it, then left click on the palemoon folder, scroll on down to the subfolder named "palemoon", right click on it and when the box pops open, left click on "execute" and it will run. If you backup your Firefox bookmarks, you can restore them and drop them onto the Pale Moon Bookmarks Toolbar. If you like it, then you can install it by making a menu entry and a launcher for it. If you don't like it, then just delete the main palemoon folder which was extracted from the tarball and everything is gone.
I use the linux Pale Moon browser in both Mint 16 (XFCE) and SolydX. It gives me the old Firefox look and brings back what Mozilla has taken out of Firefox. I've been using Windows only Pale Moon in Windows 7 since version (4.0). In Windows and now in linux, Pale Moon is my default browser.
One last note. Firefox and Pale Moon "do not share the same profile" so you can run both browsers at the same time without any problems so you can compare them against each other.