CSS production of three-dimensional navigation bar, the implementation code is as follows:
<!doctype html>：
Summarize:
1. Body part with unordered list
2, (1) hover
The effect when the mouse moves over.
(2) Questions:: Before and: the difference between before
In simple terms, a single colon (:) used for CSS3 pseudo-classes, double colons (::) for CSS3 pseudo-elements.
Specifications for CSS Selectors:
A Pseudo-element is made of both colons (::) followed by the name of the pseudo-element.
This:: Notation are introduced by the current document in order to establish a discrimination between pseudo-classes and P Seudo-elements. For compatibility with existing style sheets, user agents must also accept the previous One-colon notation for Pseudo-elem Ents introduced in CSS levels 1 and 2 (namely,: First-line,: First-letter,: Before And:after). This compatibility isn't allowed for the new pseudo-elements introduced in CSS level 3.Simple translation: Pseudo-elements consist of double colons and pseudo-element names. Double colons are introduced in the current specification to differentiate between pseudo-classes and pseudo-elements. However, the browser needs to support the old existing pseudo-elements, such as: First-line,: First-letter,: Before, after, and the new pseudo-element introduced in CSS3 does not allow the old single colon to be supported.
Now you can answer the questions in the title completely, for the pseudo-elements that existed before CSS2, such as: before, single colon and double colon: the Before function is the same.
Therefore, if your site only need to be compatible with WebKit, Firefox, Opera and other browsers, it is recommended that the pseudo-elements of the use of double colons, if you have to be compatible with IE browser, or with CSS2 single colon is more secure.
Summarize
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