What is the CSS that browsers use as default for HTML elements?

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Browsers use a set of default CSS rules for HTML elements called the user agent stylesheet. The specifics of these rules can vary between browsers, but some common examples include:

• Most elements have a margin and/or padding of 0 by default.
• Some elements, such as the body and heading elements, may have default font sizes, colors, and/or styles applied to them.
• Links and visited links may have default colors applied to them.
• Lists and table elements may have default styles and/or spacing applied to them.

These default styles are intended to provide a baseline look and feel for web pages, but web developers can override them with their own custom CSS rules.