what is css3

css3 is an upgraded version of CSS technology. It was formulated in 1999. On May 23, 2001, W3C completed the working draft of CSS3, which mainly includes box model, list module, hyperlink method, language module, and background. and modules such as borders, text effects, and multi-column layout.

The operating environment of this article: Windows7 system, HTML5&&CSS3 version, DELL G3 computer

CSS3 introduction:

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

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.

Advantages of CSS3:

1. Reduce development costs and maintenance costs

Before the emergence of CSS3, in order to achieve a rounded corner effect, developers often You need to add additional HTML tags and use one or more images to complete it, while using CSS3 only requires one tag and can be completed using the border-radius property in CSS3. In this way, CSS3 technology can free people from the work of drawing, cutting and optimizing images. If you need to adjust the curvature or color of the fillet later, using CSS2.1, you need to draw and cut the image from scratch to achieve it. Using CSS3, you only need to modify the border-radius attribute value to quickly complete the modification.

The animation features provided by CSS3 allow developers to stay away from JavaScript when implementing some dynamic buttons or dynamic navigation, so that developers do not need to spend a lot of time writing scripts or looking for suitable script plug-ins to adapt. Some dynamic website effects.

2. Improve page performance

Many CSS3 technologies have become "replacements" for images by providing the same visual effects. In other words, when doing Web development, reduce redundant tag embedding. The number of sets and images used means that users will have to download less content and the page will load faster. In addition, fewer images, scripts and Flash files can reduce the number of HTTP requests when users visit the website, which is one of the best ways to improve page loading speed. Using CSS3 to create a graphical website does not require any images, which greatly reduces the number of HTTP requests and improves the page loading speed. For example, the CSS3 animation effect can reduce HTTP requests for JavaScript and Flash files, but it may require the browser to perform a lot of work to complete the rendering of the animation effect, which may cause the browser to respond slowly and cause user loss. Therefore, you need to think carefully when using some complex special effects. In fact, many CSS3 technologies can greatly improve page performance under any circumstances.

CSS3 will be fully backwards compatible, so no design modifications are necessary to make them continue to work. Web browsers will also continue to support CSS2.

Recommended study: "css3 video tutorial"

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