User style sheets allow you to control how Web pages that you visit look. This is especially useful if you have accessibility issues. But it's also helpful if you just want to avoid seeing annoying things like the <blink> tag or <marquee>.
What is a User Style Sheet?
A user style sheet is exactly like any other style sheet you might write. It is simply a text file with CSS declarations in it to affect properties that might be found on Web pages. You can use any CSS style property in a user style sheet.
Remember that user style sheets have a lower weight than author style sheets, so if you want to be sure to have your styles show up always, use the !important declaration.
Editing Your User Style Sheet
Editing your user style sheet depends upon which browser you are using. Here are instructions for some of the more popular Web browsers: