Not surprised that it doesn't work for Firefox because Firefox is so lame.

It can not Grayscale mode.
Not found Grayscale button.
No color design.
サイトごとにグレースケール表示をかんたんに切り替えできると思いましたが、そうではありませんでした。
グレースケールボタンはどこにもない。
このアドオンの画面は色彩設計がされていません。目が痛い。

Great Extension! One thing i would wish is a more structured font-management.

it feels pretty chaotic insering all fonts in just one line.
Maybe also integrate custom categories for the fonts.

I love this addon but when i ask google a question i keep getting a white page ad i dont like it :(

I never write reviews. But this extension is gold. I created account just to say thank you.

Update: My firefox was broken. The extension works fine.