How to learn CSS?


What is CSS?
CSS (Cascading Style Sheet, Cascading Style Sheet) is created and maintained by the CSS Working Group of W3C (World Wide Web Alliance). It is a markup language that can be directly executed by browsers without compiling and is used to control the appearance of Web pages. By using CSS style to control the attribute display of each element of the page, the content of the page can be separated from its presentation.

The History of CSS
As a W3C recommendation, CSS1 was released on December 17, 1996. This recommendation was revised on 11 January 1999.
As a W3C recommendation, CSS2 was released on January 11, 1999. CSS2 adds support for media (printers and auditory devices) and downloadable fonts.
CSS3 plans to divide CSS into smaller modules.

Advantages of CSS
1 Avoid unnecessary HTML code and reduce the amount of code.
2 Shorten update and maintenance time
3 Make special effects that HTML can’t achieve

CSS Writing Specification
Selector: The so-called selector is the element in the rule that is used to select the style to be applied in the document. This element can be a tag in (X) HTML, or a class (class) or ID attribute-qualified tag specified in the page.
Declarations: Declarations are enclosed in a pair of braces “{}” to tell browsers how to render objects that match selectors on a page. The declaration is composed of attributes and their attribute values, separated by colons and terminated by semicolons. The declaration can be in the form of a combination of one or more attributes.
Property: Attributes are agreed upon by official CSS specifications, not customized, except for individual browser private attributes.
Attribute value: Attribute value is placed after the attribute name and colon. Specific content follows the category of the attribute and presents different forms, generally including values, units and keywords.

HTML and CSS Course Recommendation: Aliyun University – Developer Classroom