#8.8.16Summary# Difficulty: relationship selector-HTML Tutorial-php.cn

1.What is CSS?

CSS(Cascading Style Sheets):Cascading Style Sheets, a style design language that separates web page presentation from content.

2. What can CSS do?

a. Some animation effects

b.Page layout

c. Control the theme of the entire website

3. CSS syntax structure?

4. How to introduce CSS?

a. Inline Write the CSS style code directly in the HTML code

<span style="color: #0000ff;"><</span><span style="color: #800000;">p </span><span style="color: #ff0000;">style</span><span style="color: #0000ff;">="color:#F00;"</span><span style="color: #0000ff;">></span>这里文字是红色<span style="color: #0000ff;"></</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>

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b. Embedded Write the CSS style code between the tags, Generally, the embedded css style is written between

<span style="color: #0000ff;"><</span><span style="color: #800000;">style </span><span style="color: #ff0000;">type</span><span style="color: #0000ff;">="text/css"</span><span style="color: #0000ff;">></span><span style="background-color: #f5f5f5; color: #800000;">
span</span><span style="background-color: #f5f5f5; color: #000000;">{</span><span style="background-color: #f5f5f5; color: #ff0000;">
      color</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;">red</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
       <span style="background-color: #f5f5f5; color: #000000;">}</span>
<span style="color: #0000ff;"></</span><span style="color: #800000;">style</span><span style="color: #0000ff;">></span>

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c.External style css style, written in a separate file

<span style="color: #0000ff;"><</span><span style="color: #800000;">link </span><span style="color: #ff0000;">href</span><span style="color: #0000ff;">="appearance.css"</span><span style="color: #ff0000;"> rel</span><span style="color: #0000ff;">="stylesheet"</span><span style="color: #ff0000;"> type</span><span style="color: #0000ff;">="text/css"</span> <span style="color: #0000ff;">/></span>

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5. CSS Priority

a. The weights are the same Proximity principle (the closer to the element being set, the higher the priority)

Priority: Inline > Embedded > External (Premise: The position of the embedded css style must be behind the external style. )

b. The weights are different

A. The maximum weight of inline style sheets is 1000
B. The weight of the ID selector is 100
C. The weight of the Class class selector is 10
D. The HTML tag selector has a weight of 1

CSS priority rule:

A Each selector has a weight, the greater the weight, the higher the priority

B When the weights are equal, the style sheet settings that appear later are better than the style sheet settings that appear first

C The rules of creators are higher than those of viewers: that is, the CSS styles set by web page writers have priority over the styles set by browsers

D The inherited CSS style is not as good as the CSS style specified later

E In the same set of attribute settings, the rule marked with "!important" has the highest priority

6. CSS comments

a. Single line comment code //...

<span style="color: #800000;">//我是一个萌萌哒小男孩！</span>

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b.Multi-line comment code /*...*/

<span style="color: #008000;">/*</span><span style="color: #008000;">我是一个萌萌哒
小男孩！
嘿嘿嘿~</span><span style="color: #008000;">*/</span>

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7. Selector

a. Wildcard selector

The wildcard character is represented by an asterisk *, which means "all".

For example: * { color : red; } Here, set the font of all elements to red.

b. Element selector

If you want to style HTML, the selector is usually an HTML element, such as p, h1, em, a, or even html itself

c. Group selector

Usually when there are several places in a CSS style that need to use the same settings, writing them one by one is a tiring job, too repetitive and lengthy, and difficult to manage. In CSS, you can merge these selectors with the same settings, apply the same definition to multiple selectors, and combine the selectors into groups separated by commas. For example: p,div,a{color:red;}

d. Relationship selector

A. DIV P

元素中所有

元素

B. DIV>P

元素中所有直接子元素

C.DIV+P 所有位于

元素后的第一个

元素

D.DIV~P

元素的所有相邻兄弟元素

举例：

A.DIV P

<span style="color: #0000ff;"><!</span><span style="color: #ff00ff;">DOCTYPE html</span><span style="color: #0000ff;">></span>
<span style="color: #0000ff;"><</span><span style="color: #800000;">html </span><span style="color: #ff0000;">lang</span><span style="color: #0000ff;">="en"</span><span style="color: #0000ff;">></span>
<span style="color: #0000ff;"><</span><span style="color: #800000;">head</span><span style="color: #0000ff;">></span>
    <span style="color: #0000ff;"><</span><span style="color: #800000;">meta </span><span style="color: #ff0000;">charset</span><span style="color: #0000ff;">="UTF-8"</span><span style="color: #0000ff;">></span>
    <span style="color: #0000ff;"><</span><span style="color: #800000;">title</span><span style="color: #0000ff;">></span>关系选择符<span style="color: #0000ff;"></</span><span style="color: #800000;">title</span><span style="color: #0000ff;">></span>
    <span style="color: #0000ff;"><</span><span style="color: #800000;">style </span><span style="color: #ff0000;">type</span><span style="color: #0000ff;">="text/css"</span><span style="color: #0000ff;">></span><span style="background-color: #f5f5f5; color: #800000;">
        div p</span><span style="background-color: #f5f5f5; color: #000000;">{</span><span style="background-color: #f5f5f5; color: #ff0000;">
            color</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;">#FFFF00</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
        <span style="background-color: #f5f5f5; color: #000000;">}</span>
    <span style="color: #0000ff;"></</span><span style="color: #800000;">style</span><span style="color: #0000ff;">></span>
<span style="color: #0000ff;"></</span><span style="color: #800000;">head</span><span style="color: #0000ff;">></span>
<span style="color: #0000ff;"><</span><span style="color: #800000;">body</span><span style="color: #0000ff;">></span>
<span style="color: #0000ff;"><</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>我是第一段<span style="color: #0000ff;"></</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>
    <span style="color: #0000ff;"><</span><span style="color: #800000;">div</span><span style="color: #0000ff;">></span>
        <span style="color: #0000ff;"><</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>我是第二段<span style="color: #0000ff;"></</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>
        <span style="color: #0000ff;"><</span><span style="color: #800000;">span</span><span style="color: #0000ff;">><</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>我是第三段<span style="color: #0000ff;"></</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></</span><span style="color: #800000;">span</span><span style="color: #0000ff;">></span>
    <span style="color: #0000ff;"></</span><span style="color: #800000;">div</span><span style="color: #0000ff;">></span>
    <span style="color: #0000ff;"><</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>我是第四段<span style="color: #0000ff;"></</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>
<span style="color: #0000ff;"><</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>我是第五段<span style="color: #0000ff;"></</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>
<span style="color: #0000ff;"><</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>我是第六段<span style="color: #0000ff;"></</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>
<span style="color: #0000ff;"></</span><span style="color: #800000;">body</span><span style="color: #0000ff;">></span>
<span style="color: #0000ff;"></</span><span style="color: #800000;">html</span><span style="color: #0000ff;">></span>

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B.DIV>P

  <span style="color: #0000ff;"><</span><span style="color: #800000;">style </span><span style="color: #ff0000;">type</span><span style="color: #0000ff;">="text/css"</span><span style="color: #0000ff;">></span><span style="background-color: #f5f5f5; color: #800000;">
        div>p</span><span style="background-color: #f5f5f5; color: #000000;">{</span><span style="background-color: #f5f5f5; color: #ff0000;">
            color</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;">#FFFF00</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
        <span style="background-color: #f5f5f5; color: #000000;">}</span>
    <span style="color: #0000ff;"></</span><span style="color: #800000;">style</span><span style="color: #0000ff;">></span>

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C.DIV+P

<span style="color: #0000ff;"><</span><span style="color: #800000;">style </span><span style="color: #ff0000;">type</span><span style="color: #0000ff;">="text/css"</span><span style="color: #0000ff;">></span><span style="background-color: #f5f5f5; color: #800000;">
        div+p</span><span style="background-color: #f5f5f5; color: #000000;">{</span><span style="background-color: #f5f5f5; color: #ff0000;">
            color</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;">#FFFF00</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
        <span style="background-color: #f5f5f5; color: #000000;">}</span>
    <span style="color: #0000ff;"></</span><span style="color: #800000;">style</span><span style="color: #0000ff;">></span>

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D.DIV~P

<span style="color: #0000ff;"><</span><span style="color: #800000;">style </span><span style="color: #ff0000;">type</span><span style="color: #0000ff;">="text/css"</span><span style="color: #0000ff;">></span><span style="background-color: #f5f5f5; color: #800000;">
        div~p</span><span style="background-color: #f5f5f5; color: #000000;">{</span><span style="background-color: #f5f5f5; color: #ff0000;">
            color</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;">#FFFF00</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
        <span style="background-color: #f5f5f5; color: #000000;">}</span>
    <span style="color: #0000ff;"></</span><span style="color: #800000;">style</span><span style="color: #0000ff;">></span>

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#8.8.16总结# 难点：关系选择符

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