Understanding of HTML tag elements and CSS pseudo-class and pseudo-elements

Tags: that should all be known. <br/>, <a>, <p></p> and so on are all labels.

elements: the label starts to the end. For example:the content between <p>p <p/> , the red part is the element.

The content of the element: the portion between the beginning and end of the label, the "content between P " in the red section above, which is the content of the element.

pseudo-Class: the element that is specific to the state.

pseudo-element: The content of the element .

Pseudo-elements and pseudo-classes are difficult to distinguish, because they are similar in effect, and css3 in order to distinguish between the two, it is clear that the pseudo-class is represented by a colon, while the pseudo-element is represented by two colons.

syntax for pseudo-class:selector:pseudo-class {property:value;}

Syntax for pseudo-elements: selector::p seudo-element {property:value;}

But because of compatibility issues, most of the time is still a single colon.

Reference:

Http://www.cnblogs.com/springliang/p/6202600.html

http://blog.csdn.net/sadfishsc/article/details/7047595

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Understanding of HTML tag elements and CSS pseudo-class and pseudo-elements