User-agent style
A user-agent style is a default set of presentation rules supplied by a browser for rendering document elements when author styles do not override them.
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Browser default styles are built-in CSS styling values that a browser applies to HTML elements when no author styles override them.
- How it is used
- Establishes the baseline appearance of HTML elements before theme, site, or inline CSS modifies them.
- How deep it goes
- Defines default property-value pairs and the four-level cascade, but stops short of browser-specific implementation details.
- Examples
- Uses h1 display, size, margins, weight, and color defaults as concrete examples.
- What you can do after
- Evaluate why an HTML element looks a certain way and apply CSS that overrides its browser defaults.
Tiny CSS Projects
Default styles are the initial presentation rules applied by a browser or operating system when author styles do not override them.
- How it is used
- Establishes readable fallback presentation for HTML and supplies the baseline that author CSS overrides.
- How deep it goes
- Defines the stylesheet origin, priority, common properties, and platform variation, but stops short of detailing browser implementations.
- Examples
- Uses headings, form controls, progress bars, and fieldsets to show defaults, variation, and practical resets.
- What you can do after
- Apply CSS resets and overrides while anticipating browser differences in native controls.
CSS in Depth, Second Edition
The rendering defaults supplied by a web browser through its user-agent stylesheet.
- How it is used
- Explains the browser defaults that shape unstyled elements and the CSS overrides used to establish an intended page design.
- How deep it goes
- Explains stylesheet origins, priority, common defaults, overrides, and revert, without descending into browser implementation internals.
- Examples
- Uses headings, paragraphs, lists, links, and a styled navigation bar to demonstrate defaults and deliberate overrides.
- What you can do after
- Apply it via CSS by identifying browser defaults, overriding unwanted values, and restoring selected defaults with revert.
Read how CSS in Depth, Second Edition explains user-agent style →
Related concepts
- margin propertyconfigures · The CSS margin property specifies the outer space around an element’s border, separating it from neighboring content.
- browserproduced by · A web browser is software that retrieves, interprets, and renders web resources, executes supported web content, and enables interaction with web pages and applications.
- display propertyconfigures · The CSS display property specifies how an element participates in layout and the type of box it generates.
- stylesheetkind of · A stylesheet is a text document containing CSS rules that specify the visual presentation of structured documents and their elements.
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