How does one get the thing to work. Thought I installed it, but it don't do anything. Am I doing something wrong?

I love this extension, however it slows down my browser.

Major eye-saver, 5 star add on except the performance hit on Gmail. Work around by adding mail.google.com to the exception list.

takes like a million years to load up

Works beautifully, even on Facebook. Kudos to the developers

love the options and darkening of css keeping colors but better for dark backgrounds and not just inverting everything.

I've tried to give this add-on a chance twice. But, sorry, can't do it. It breaks Firefox constantly.