Here is my first Add-On. I searched 'Black' into the search bar on the site and there it was. I downloaded it and I was very impressed. Hope you all like it too. Heres the link : https://addons.mozilla.org/en-US/firefox/addon/9304 Here is my second Add-On. It makes the tabs seem like Windows but on the internet. I was also impressed with this and would recommend it. I sort of envied CarlT2001 (My Uncle) because my graphics card cannot handle the Windows thing. Heres the link: https://addons.mozilla.org/en-US/firefox/addon/8253
If you're new to Firefox, let me tell you that the first thing that you've shown is a theme and the second one is an add-on. I'm telling you this, just in case you want to get more themes or add-ons, so you'll know what you're really looking for.