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This article is to share with you about what css double colons mean. The editor thinks it is very practical, so share it with you as a reference and follow the editor to have a look.

What does the double colon of css mean?

Css double colons are pseudo elements. Pseudo elements control the same content as an element, but pseudo elements do not exist in the document tree and are not real elements, so they are called pseudo elements.

Pseudo elements are:: first-line,:first-letter,:before,:after (it should be an error in understanding that first-line,:first-letter is listed as a pseudo class in the CSS2.0 Chinese manual compiled by Su Shen Xiaoyu)

Reminder, if your site only needs to be compatible with webkit, firefox, opera and other browsers, it is recommended to use double colons for pseudo elements. If you have to be compatible with IE browsers, it is safer to use CSS2 single colons.

Unlike pseudo-class elements that aim at a special state, pseudo-elements operate on specific content in the element, and they operate at a deeper level than pseudo-classes, so they are much less dynamic than pseudo-classes.

In fact, the purpose of designing pseudo-elements is to select the first word (letter) and the first line of the content of the element, and to select tasks that cannot be done by ordinary selectors such as before or after the content.

The content it controls is actually the same as the element, but it is only an abstraction based on the element and does not exist in the document, so it is called pseudo-element.

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