Edit CSS
Sometimes, you can find a very interesting web page, but the display is bad, especially for shining and incompatible colors, or very small fonts, …
EditCSS can fix this, but only for you: after installing the Firefox extension, right click anywhere in the page, and tick “Edit CSS” option; it will open a side bar with a text area; there, you can code with CSS, which will overwrite the default display.
Finally, you can save your code as a CSS file, and if you really screwed the code up, just close the editable area and refresh the page. 
