files/en-us/web/css/reference/properties/index.md
A CSS property is a parameter used in a CSS declaration that lets you style certain aspects of selected elements. For example, the {{CSSxRef("opacity")}} property is used to set the opacity of a selected element, allowing you to control if content behind that element is visible:
/* Set 0.8 opacity on elements */
img {
opacity: 0.8;
}
Each property has a name (e.g., opacity), a value (e.g., 0.8), and a defined behavior on the rendering of the document.
CSS also defines shorthand properties, so you can specify multiple related properties in a single declaration.
For example, the {{CSSxRef("margin")}} property is a shorthand for {{CSSxRef("margin-top")}}, {{CSSxRef("margin-right")}}, {{CSSxRef("margin-bottom")}}, and {{CSSxRef("margin-left")}}, setting the margin of all four sides of an element:
/* Give elements 1rem of margin */
img {
margin: 1rem;
}
selector {
property: value;
}
Standard properties defined by CSS specifications include the following:
Non-standard vendor-prefixed properties include:
-moz- prefix-webkit- prefix{{Specifications}}