html css3 what is

CSS3 is an upgraded version of CSS (Cascading Style Sheets) 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, and 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.

Development Process

As early as 2001, W3C completed the draft specification of CSS3. A new feature of the CSS3 specification is that it is divided into several independent modules. On the one hand, dividing it into several smaller modules is more conducive to the timely updating and release of specifications, and the timely adjustment of module content. These modules are independently implemented and released, which also lays the foundation for future CSS expansion. On the other hand, due to limitations of supported devices and browser manufacturers, there is no equipment or manufacturers can selectively support some modules and support a subset of CSS3, which is conducive to the promotion of CSS3.

Programming development

CSS3 programming tool is the same as CSS. Any text editing tool can be used for writing, such as: Wordpad, Notepad under Windows; or others Tools specifically used for editing web page text, such as: IntelliJ IDEA, Eclipse, MyEclipse, webstorm, sublime text; in addition, there are also plug-ins specifically for front-end development, such as: Emmet.

Language Basics

The syntax of CSS3 is based on the original version of CSS. It 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. Stylesheet .

Advantage evaluation

1. Reduce development costs and maintenance costs

Before the emergence of CSS3, developers wanted to implement a The rounded corner effect often requires adding additional HTML tags and using one or more images to complete, while using CSS3 only requires one tag and can be completed using the border-radius attribute 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 , reducing redundant tag nesting and the number of 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 significantly improve page performance under any circumstances [44] .

CSS3 will be fully backwards compatible, so there will be no need to modify the design to make them continue to work. Web browsers will also continue to support CSS2

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