Content, padding, border, and margin make up the box model.

Relative moves from original position; absolute positions relative to nearest positioned ancestor.

id is unique; class can be reused.

visibility hides but keeps space; display removes element from layout.

Minify files, reduce specificity, and remove unused styles.

Overrides all other declarations, regardless of specificity.

Use margin: auto or flexbox/grid techniques.

Allow responsive design by applying styles based on screen size or device.

Define relationships between selectors: descendant ( ), child (>), adjacent (+), sibling (~).

Tools like SASS or LESS add features like variables and nesting to CSS.

Targets part of an element, like ::before or ::after.

Use @import "filename.css"; at the top of the file.

Controls stacking order of overlapping elements.

Forces a property to inherit value from parent.

Static — not affected by top, bottom, left, or right.

Use universal selector * or define styles in body/root.

em is relative to parent; rem is relative to root element.

Inline, internal (embedded), and external CSS.

A layout model for arranging elements in rows or columns with flexible sizing.

Targets elements in a specific state, like :hover or :nth-child().

Use fluid layouts, media queries, and relative units.

CSS styles HTML elements to control layout, color, fonts, and responsiveness.

Reusable custom property values, declared with --var-name.

Determines which rule applies when multiple rules target the same element.

Performs calculations to dynamically set CSS property values.