A selector that specifies CSS styles for a group of elements
In a style sheet, a format instruction that consists of a specified selector and the properties and values applied to it.
In CSS, the arrangement of content elements on a page and how the space is used.
A selector that specifies CSS styles for one unique element.
Defines the file type, such as text or video, and the extension, such as css or mp4, for a user agent or browser.
A descriptive characteristic of an object (such as color, width or height) that the developer stipulates in the creation of the object.