Definitions: User Agent, User, and Author

It’s important to understand the distinction between the terms “user agent,” “user,” and “author” when discussing CSS’s cascade.

A user agent, or UA, refers to any browser when the term is used to discuss web-based technologies. Firefox, Chrome, and Opera are all user agents.

A user is synonymous with a computer user. For example, I visit every web page on the Internet as a user.

And finally, when I write CSS code, I am wearing the hat of an author. Similarly, when I write an HTML, I am the author of that document.