Very few working themes, most of them are out of date and either doesnt work or brakes the websites.

I like this plugin, but I want it too in mobile version of Firefox because some websites aren't responsive. Can you create a version for mobiles?

Brilliant, allows me to customize my most visited sites exactly how I want. Most of all it lets me live in my world of Dracula.

Used Stylish for ages, don't know why I didn't switch sooner. Besides not having the shady past of it's older counterpart, the coding environment is so much nicer, live preview, syntax autocomplete, colour pickers, customisable UI/UX.

I used this to remove rounded edges on YouTube thumbnails (why?) that obscured Thumbnail Rating Bar for YouTube (a different Add-on). Thank you!

I'm using this to bring back youtube Red Subscribe Button

Quand les bloqueurs de pubs ne suffisent plus, ou simplement pour améliorer une mise en page pour qu'elle colle mieux à des besoins précis.
Du coup il est préférable de savoir manipuler les CSS de façon poussée, mais l'on n'a pas rien sans rien !!