It worked in the session when I first installed it, but in the next session and thereafter, it didn't.

excelente ideal para evadir scripts de video HD sin sentido y mejorar la latencia de red

This add-on is quite comprehensive: Anything from lowering video quality to disabling CSS animations.

Some options are somewhat confusing, like what's the difference between "page activated" and "website activated"?

Some options are not working, like lowering video quality on Youtube.

This should be by default in any browser.