1. How CSS works_html/css_WEB-ITnose

CSS stands for Cascading Style Sheets. It is an application used to express HTML (an application of Standard Generalized Markup Language) or XML (a subset of Standard Generalized Markup Language). Computer language for file formats. It is a style design language that can truly separate web page performance and content. It can perform pixel-level precise control over the position and typesetting of objects in web pages. It supports almost all font sizes and styles, and has the ability to edit web page objects and model styles. Ability and ability to carry out preliminary interaction design, it is currently the best performance design language based on text display.

CSS rules

CSS documents are composed of a series of rules. A CSS rule is actually a CSS instruction. This instruction first selects HTML elements and then sets the style of the selected elements

The following is a simple CSS rule that sets the paragraph background color to green

p{background-color: green}

CSS Basic Rules

A CSS rule consists of two parts: selector declaration

Selector: Indicates the element to be selected

Statement: It consists of attributes and values. The attribute indicates which aspect of the style affects the element. The value is actually a state of the attribute

In the above example, it can be seen that a rule from left to right is: selector, left curly brace, attribute, colon, value, right curly brace

Extension of the basic rule 1: Multiple declarations are included in In a rule

p{color: green;font-size: 45px;font-weight: bold}

add a semicolon after each statement to show separation

Extension 2 of the basic rule: multiple selector combinations Together

h1,h3,p{color: green;font-size: 45px;font-weight: bold}

Separate commas between selectors
Extension 3 to basic rules: multiple rules apply to the same selector

h1,h3,p{color: green;font-size: 45px;font-weight: bold}

Now we want the background color of the p paragraph to be blue, we can continue to add a rule

p{background-color: blue}

CSS selector classification

All There are three types of selectors used to select specific elements: context selectors, ID and Class selectors, attribute selectors

Context selectors