The goal of the XHTML standard is to replacehtml. According to the W3C, "XHTML is the successor tohtml" (http://www.w3.org/MarkUp/).
XHTML has two major goals:
Create a clearer separation between document structure and presentation.
An application that re-representshtmlas XML.
The advantage of using the XHTML standard is that you only need to design a page once and have it display and work exactly the same way in any modern browser. For example, when generated to standards, pages display the same way in Internet Explorer, Mozilla Firefox, Netscape Navigator, Opera, Camino, and Safari without any additional work. And the XHTML standard can make Web sites more accessible to devices such as smartphones and computers for people with disabilities.
The XHTML standard requires the creation of a clearer separation between document structure and presentation. Therefore using CSS style sheets is essential. CSS occupies a very important position in web pages, and its use has always been a hot topic of discussion. CSS is the abbreviation of Cascading Style Sheet, which is translated as "cascading style sheet". When the W3C promulgated the HTML4 standard in 1997, it also announced the first standard CSS1 for style sheets. After the CSS1 version, the CSS2 version was released in May 1998.
The intent of the inventors of CSS was to remove the presentational element, i.e. content should be marked up based on what it represents, and stylesheets should be used to beautify the content. This is consistent with XHTML's goal of separating document structure and presentation (the b , i and img tags (as well as big , small and tt ) will be removed in XHTML 2.0, and even the use of br will be deprecated from a future release) Get rid of it. The reason is that most markup is presentational. Their only purpose is to give the browser instructions about how its content should be displayed, but provides absolutely no information about what its content is.) So they became The best partner. For more information about XHTML2.0, please see: http://www-128.ibm.com/developerworks/cn/xml/x-wa-xhtml/index.html
CSS used to be often It is used to define the properties of fonts, and now in the new standard we will use it to control the display of the entire page. However, we must do something different from the past to adapt to this new change, such as: using p for layout instead of tables, using structured, semantic tags, etc. Thanks to the new processing method, we can now easily design reusable CSS (the same style file is used in multiple WEB sites) and skinnable WEB sites (one site uses multiple different styles).
For an example, please seeSichuan Provincial Department of Construction Information Portal. The interface is switched on the upper right, as shown in Figure 1. Due to time reasons, it has not passed XHTML and CSS verification, but the principle is the same.
Figure 1: Interface style switching