Is there any difference between css3 code and css?

Different: css3 is an upgraded version of css technology. Some new attributes and selectors are added to css3, which can make website development better and more convenient, such as rounded corners, shadows, gradients, media queries, " :root" selector, etc. CSS3 has compatibility issues, and some attributes need to be added with browser-specific prefixes for support, such as "-ms-".

The operating environment of this tutorial: windows7 system, css3 version, Dell G3 computer.

(Learning video sharing: css video tutorial)

CSS3 is an upgraded version of CSS (Cascading Style Sheet) technology. It was formulated in 1999 and May 2001. On the 23rd, W3C completed the working draft of CSS3, which mainly includes modules such as box model, list module, hyperlink method, language module, background and border, text effects, and multi-column layout.

One of the major changes in the evolution of CSS is the W3C's decision to break CSS3 into a series of modules. Browser vendors innovate quickly at the pace of CSS, so by taking a modular approach, elements in the CSS3 specification can move forward at different speeds because different browser vendors only support given features. But different browsers support different features at different times, which also complicates cross-browser development.

CSS3 syntax

CSS3 syntax is based on the original version of CSS, which allows users to specify specific HTML elements in tags without using redundant class, ID or JavaScript. Most of the CSS selectors are not new in CSS3, but were not widely used in previous versions. If you want to try to achieve a clean, lightweight tag and better separation of structure and performance, advanced selectors are very useful. They can reduce the number of classes and IDs in the tag and make it easier for designers to maintain. Style sheet.

The new selectors are shown in the following table:

## Matches the root element of the document. In HTML (an application under Standard Universal Markup Language), the root element is always HTML##E:nth-child(n)E:nth-last-child(n)##E:nth-of-type(n) that is the only child element in the parent element # which is the only sibling element of the same type #E::selection Match the part of the E element that is selected or highlighted by the userNegative pseudo-classE:not(s) Matches all that are not Elements matching simple selector s EUniversal sibling element selectorE ~ FMatch the F element after the E element

Selector type	Expression Formula	##Description
Attribute selector for substring matching	E[att^="val"]	Matches E elements that have the att attribute and whose value starts with val
	E[att$="val"]	Matches E elements that have the att attribute and whose value ends with val
	E[att*="val"]	Matches E elements with att attribute and value containing val
Structural pseudo-class	E:root
	Matches the nth child element E
	Matches the n-th structural child element from the bottom of the parent element E
	Matches the nth sibling element E	##E:nth-last-of-type(n)
	Matches the nth sibling element from the bottom of the same type E	E:last-child
	Match the last E element in the parent element	E:first-of-type
	Match the first E element among sibling elements
	E:only-child	Matches E
	E:only-of-type	Matches E
	##E:empty	Matches elements E
that do not have any child elements (including text nodes) Target pseudo-class	E:target	Matches the E element pointed to by the relevant URL
UI element status pseudo-class	E:enabled	Matches all user interfaces (form forms) that are in an available state E element
	E:disabled	matches E that is in a disabled state in all user interfaces (form forms) Element
	E:checked	matches the selected element E## in all user interfaces (form forms)

css3 new features

css3 new It has many features, such as rounded corners, graphical borders, block shadows and text shadows, using RGBA to achieve transparency effects, gradient effects, using @Font-Face to achieve customized fonts, multiple background images, text or image deformation processing (rotation, zoom, tilt, move), multi-column layout, media queries, etc.

Compatibility issues

Browser manufacturers have been implementing CSS3 before. Although it has not become a true standard, it provides browser-specific prefixes:

Chrome (Google Chrome): -webkit-
Safari (Safari): -webkit-
Firefox (Firefox browser): -moz-
lE (IE browser): -ms-
Opera (Opin Browser): -0-
For example, CSS3 gradient styles are different in Firefox and Safari. Firefox uses -moz-linear-gradient and Safari uses -webkit-gradient, both of which use the vendor type prefix.

It should be noted that when using styles with manufacturer prefixes, you should also use styles without prefixes. This ensures that when the browser removes the prefix and uses the standard CSS3 specification, the style will still be valid. For example:

#example{
  -webkit-box-shadow：0 3px 5px#FFF;
  -moz-box-shadow：0 3px 5px#FFF;
  -o-box-shadow：0 3px 5px#FFF;
  box-shadow：0 3px 5px#FFF;/*无前缀的样式*/
}

CSS3 browser compatibility:

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