CSS pseudo-Class (pseudo-classes)

Summary: Pseudo-Class (Pseudo classes) is a bolt of a selector that specifies the state of one or its associated selectors. They are in the form of Selector:pseudo class {Property:value;}, and simply use a half-width colon (:) to separate the selectors from the pseudo-class. CSS Many of the suggestions are not supported by the browser, but there are four can be safely used on the hyperlink on the pseudo-class.

: Link is used on an unreachable connection.

: The visited is used on connections that have already been visited.

: Active is used to get the focus (for example, clicked) on the connection.

: hover is used for the connection on which the mouse cursor is placed.

Application scenarios: For example a tag shows different colors in different states

a:link {color: #FF0000}
a:visited {color: #00FF00}
a:hover {color: #FF00FF}
a:active {color: #0000FF}

Need to be aware

Tip: In CSS definitions, a:hover must be placed after A:link and a:visited to be valid.

Hint: In the CSS definition, a:active must be placed after a:hover to be valid.

Tip: The pseudo-class name is not case sensitive.

There are also some common such as: First-child (the application scenario such as the first element of Li and other elements of the style is not the same)

Reference

1.http://www.w3school.com.cn/css/css_pseudo_classes.asp

CSS pseudo-Class (pseudo-classes)