Very light-weight add-on to inject CSS to decorate the page as you want. It can hide annoying elements like fixed headers or make them scroll away as you scroll. No rules are included by default. Go to the Options page from the add-on manager and add rules. Example: On site www.example.com, set rule: body{border: 5px solid yellow !important;}. If you plan to hide elements on a page, you probably should consider Ublock Origin instead.
