What does css language mean?

css language is a computer language used to express file styles such as HTML or XML; its full English name is "Cascading Style Sheets", which means cascading style sheets; css can not only statically modify web pages, but also coordinate Various scripting languages ​​dynamically format various elements of web pages.

The operating environment of this tutorial: Windows 10 system, css3 version, DELL G3 computer

What does the css language mean?

Cascading Style Sheets (English full name: Cascading Style Sheets) are files used to express HTML (an application of Standard Generalized Markup Language) or XML (a subset of Standard Generalized Markup Language). style computer language. CSS can not only statically modify web pages, but can also cooperate with various scripting languages ​​to dynamically format various elements of web pages.

CSS can perform pixel-level precise control over the layout of element positions in web pages, supports almost all font size styles, and has the ability to edit web page objects and model styles.

css development history

In 1990, Tim Berners-Lee and Robert Cailliau jointly invented the Web. In 1994, the Web really came out of the laboratory.

Since the invention of HTML, styles have existed in various forms. Different browsers combine their own style languages ​​to provide users with control over page effects. The original HTML contained only a few display attributes.

With the growth of HTML, in order to meet the requirements of page designers, HTML has added many display functions. But as these functions increase, HTML becomes more and more complex, and HTML pages become more and more bloated. So CSS was born.

Hakun Lee proposed the original proposal of CSS in 1994. At the time, Bert Bos was designing a browser called Argo, so they decided to design CSS together.

In fact, there were already some suggestions for unifying style sheet languages ​​in the Internet industry at that time, but CSS was the first style sheet language that contained the rich meaning of "cascading". In CSS, styles in one file can be inherited from other style sheets. The reader can use his or her own preferred style in some places and inherit or "cascade" the author's style in other places. This layered approach gives both authors and readers the flexibility to add their own designs and mix in what everyone likes.

Ha Kun first proposed CSS at a conference in Chicago in 1994. CSS was proposed again at the www network conference in 1995. Boss demonstrated an example of the Argo browser supporting CSS. , Haken also demonstrated support for CSS in the Arena browser.

In the same year, the W3C organization (World WideWeb Consortium) was established. All the creative members of CSS became the W3C working group and went all out to develop CSS standards. The development of cascading style sheets was finally on the right track. More and more members were involved, such as Thomas Reaxdon of Microsoft, whose efforts eventually led to support for the CSS standard in the Internet Explorer browser. Ha Kun, Persia and others are the main technical leaders of this project. At the end of 1996, the first draft of CSS was completed. In December of the same year, the first formal standard for Cascading Style Sheets (Cascading Style Sheets Level 1) was completed and became a recommended standard by w3c.

In early 1997, the W3C working group responsible for CSS began to discuss issues not covered in the first edition. The results of the discussions formed the second edition of the CSS specification published in May 1998.

css language features

CSS provides a style description for the HTML markup language and defines the display mode of the elements. CSS is a breakthrough in the field of web design. It can be used to modify a small style to update all page elements related to it.

In general, CSS has the following characteristics:

Rich style definition

CSS provides a rich document style appearance, as well as the ability to set text and background properties; allows Create a border for any element, as well as the distance between the element's border and other elements, as well as the distance between the element's border and the element's content; allow you to freely change the capitalization, decoration, and other page effects of text.

Easy to use and modify

CSS can define the style in the style attribute of the HTML element, you can also define it in the header part of the HTML document, or you can declare the style in a special CSS file for reference in HTML pages. In short, CSS style sheets can store and manage all style declarations in a unified manner.

In addition, elements of the same style can be classified and defined using the same style, you can also apply a certain style to all HTML tags with the same name, or you can assign a CSS style to a certain in page elements. If we want to modify the style, we only need to find the corresponding style statement in the style list and modify it.

Multi-page application

CSS style sheet can be stored in a separate CSS file, so that we can use the same CSS style sheet in multiple pages. Theoretically, CSS style sheets do not belong to any page file and can be referenced in any page file. In this way, the styles of multiple pages can be unified.

Cascade

Simply put, layers are setting the same style multiple times for an element, which will use the attribute value of the last setting. For example, if you use the same set of CSS style sheets for multiple pages in a site, and if you want to use other styles for some elements in some pages, you can define a separate style sheet for these styles and apply them to the page. These later defined styles will rewrite the previous style settings, and what they see in the browser will be the style effect set in the final settings.

Page Compression

In websites that use HTML to define page effects, a large number or repeated tables and font elements are often required to form text styles of various specifications. The consequence of this is that a large number of HTML tags increase the size of the page file. Putting the style declaration separately in the CSS style sheet can greatly reduce the size of the page, so the time spent loading the page will also be greatly reduced. In addition, the reuse of the CSS style table has reduced the volume of the page to a greater extent and reduces the download time.

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