It works perfectly for nearly all sites. Would love the ability to easily specify custom colours for elements on a specific page though.

I'm browsing like ten hours a day, and this add-on takes care of my eyes. wouldn't want to be without it any more.

DARK BACKGROUND AND LIGHT TEXT is soo much better! More customizability and most importantly DOESN'T SLOW DOWN OR BREAK PAGES!
https://addons.mozilla.org/en-US/firefox/addon/dark-background-light-text/?utm_content=search&utm_medium=referral&utm_source=addons.mozilla.org

SHIVUTTAM

Slows down webpage loading by a lot
which something like Dark Background and Light Text doesn't do

Plug-in crashes pretty frequently and breaks websites. Otherwise, when it works, it works great.