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What three parts does a css style sheet consist of?

青灯夜游
青灯夜游Original
2022-05-18 17:16:305711browse

The three components of a css style sheet: 1. Selector, used to tell the browser which objects in the page the specified style will act on; 2. Properties, which are set style options provided by CSS, mainly Including font attributes, text attributes, background attributes, layout attributes, etc.; 3. Attribute value is the valid value of the specified attribute, and the attribute and attribute value are separated by ":".

What three parts does a css style sheet consist of?

# The operating environment of this tutorial: windows7 system, CSS3&&HTML5 version, Dell G3 computer.


Composition of css style sheet

The CSS style sheet includes three parts: selectors, attributes and attribute values. The syntax style is as follows: 

选择符{属性：属性值;}
The syntax description is as follows:

  • Selector (Selector): also known as selector, is a very important concept in CSS, all in HTML Markers are controlled through different CSS selectors.

    It tells the browser which objects in the page the style will act on. These objects can be a certain tag, all web page objects, specified class or id values, etc. When the browser parses this style, it renders the display effect of the object based on the selector.

  • Property: It is a set style option provided by CSS, mainly including font attributes, text attributes, background attributes, layout attributes, border attributes, list item attributes, and table attributes. etc. content. Some of these properties are only supported by some browsers, so their use becomes more complicated using CSS properties.

  • Attribute value (value): The valid value of the specified attribute. Attributes and attribute values ​​are separated by ":". When there are multiple attribute values, use ";" to separate them.

What three parts does a css style sheet consist of?

CSS selector

Commonly used CSS selectors are tag selector, category selector, inclusion selector, and ID selection. selector, class selector, etc. Use selectors to control different HTML tags to achieve various effects. The three basic selectors are introduced in detail below.

1. Tag selector

HTML page is composed of many tags, such as image tags

What three parts does a css style sheet consist of?, hyperlink tag , table tag

, etc., and the CSS tag selector is to declare which tags in the page use which CSS tags, such as a selection Device is used to declare the style of all tags in the page. For example: define a tag selector, and define the font and color of the hyperlink in the tag selector. 
<style>
	a{
		font_size:9px;
		color:#F93;
	}
</style>

2. Category Selector

Using the tag selector is very fast, but it has certain limitations. If a page declares a tag selector, all content of that tag in the page will change accordingly. There are three

tags in the join page. If you want each

to be displayed differently, you cannot use the tag selector. This is Then you need to introduce a category selector. The name of the type selector is defined by yourself and starts with ".". The defined attributes and attribute values ​​must also comply with CSS specifications. To apply the HTML tag of a category selector, simply declare it using the class attribute.
Example: 

<html>
	<style>
	.one{
			font-family:宋体;
			font-size:24px;
			color:red;
		}
	.two{
			font-family:宋体;
			font-size:16px;
			color:red;
		}
	.three{
			font-family:宋体;
			font-size:12px;
			color:red;
		}
	</style>
	</head>
	<body>
		<h2 class="one">应用选择one</h2><!--定义样式后，页面会自动加载样式-->
		<p>正文内容1</p>
		<h2 class="two">应用选择器two</h2>
		<p>正文内容2</p>
		<h2 class="three">应用选择器three</h2>
		<p>正文内容3</p>
	</body>
</html>

What three parts does a css style sheet consist of?

3.ID Selector

ID Selector The ID attribute in the HTML page is used to select and add styles. It is basically the same as the category selector. However, it should be noted that since the HTML page cannot contain two identical ID tags, the defined ID selector is also Can only be used once.

The named ID selector should start with a "#" sign, followed by the ID attribute value in the HTML tag.
For example: use ID selector to control the style in the page. 

<html>
	<style>
	#first{
			font-size:18px
		}
	#two{
			font-size:24px
		}
	#three{
			font-size:36px
		}
	</style>
	<body>
		<p id="first">ID选择器1</p>
		<p id="two">ID选择器2</p>
		<p id="three">ID选择器3</p>
	</body>
</html>

What three parts does a css style sheet consist of?

Extended knowledge: new features of CSS 3

Modules and modular structure

CSS 3 does not adopt an overall structure, but adopts a modular structure of division of labor and collaboration. This patterned structure is adopted to avoid the situation where the browser does not fully support a certain module. If the whole is divided into several modules, each browser can choose which module to support and which module to not support.

Commonly used modules in CSS 3 are shown in the following table:

Module name Function description
Basic Box Model Define various box-related modules
Line Define various line-related modules Styles
Lists Define various styles related to lists
Text Define various styles Text-related styles
Color Define various color-related styles
Font Define various font-related styles
Background and Border Define various background- and border-related styles
Paged Media Define the styles of various page element data such as headers, footers, page numbers, etc.
Writing Modes Define page Chinese The layout of this data

(Learning video sharing: css video tutorial, web front-end)

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