Summary of some knowledge points about HTML and CSS-HTML Tutorial-php.cn

Summary of some knowledge points about HTML and CSS

零下一度

Release： 2017-06-25 09:39:55

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A complete page consists of three parts:

html: Hypertext Markup Language

Through semantic tags, Build the page "structure"

css: Cascading style sheet

is responsible for the page "style" and beautify the page

js: lightweight scripting language; interaction refers to two places (behavior)

The front-end itself The "animation effect" written on the page
"data interaction" in the front and backend
The combination of structure, style, and behavior

How to introduce css

Embedded; (embedded)

<style>
    body{
        height:100%;
        background-color: red;
    }
</style>

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Inline style

<body style="height:100%; background: #333333">

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External link type (real development, all external links are used)
```
<link rel="stylesheet" href="style.css?1.1.11"/>
```
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css priority

Inline>Inline>External link

css common properties and styles

When the setting is wrong, in the chrome control There will be a yellow exclamation mark as a prompt
color: color value; there are three ways to express color
Shortcut key: c+tab

In English: red
rgb(255,0,0)
#fff

##font-size: font size

Shortcut key: fsz30->font -size:30px

font:400 14px/28px "宋体";

Picture default Is horizontal repetition and vertical repetition

background: url("images/bg2.png") no-repeat left center red;

##background-color:red

text-decoration: line-through; strikethrough
##text-decoration: none; remove underline
text-decoration: underline;Add underline
Selector in css:

1. Label selector: div p ul li dt dd em i u del strong b input label from table

##Disadvantages: Only common operations can be performed, and individual operations cannot be performed

2.class selector

3.id:
.class name

#id name
, the same page can only have one ID name; (ID names cannot be repeated)
In the real development process, class is used to set styles, and id is used to obtain elements
```
<div class="div1 div2 div3" id="div1"></div>
```
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4. Descendant selector: div p (select all p elements of descendants under the div container)

5. Child selector: div > p (select the son under the div container); compatible with IE7+
6. Intersection selector: div.div1
7. Union selector: div, p
8. Wildcard *: represents all elements
9. Order selector: compatible with IE8+
div > p:first-child

10. The next sibling selector ul li+li{} is compatible with IE7+

chrome

IE7~11

firefox
CSS inheritance and cascading
All attributes starting with font can be inherited; line-height

color can be inherited

Those starting with text can also be inherited, such as text-align
css weight
!important weight is infinite; (use less, the better)

The weight of id is greater than the weight of class

css box model
css box model consists of 5 parts ：

padding:

padding是内边距
padding的颜色和内容的颜色一致；background-color填充的是border以内的颜色
padding是复合值
padding:30px; ->pl30; pt30;pr30;pb30
padding:20px 30px; ->上下为20px 左右30px
padding:10px 20px 30px; -> 上10px 左右20px 下30px
padding:10px 20px 30px 10px; 上右下左

如果现设置padding:30px
再设置padding-left:10px
请问最后的值各是多少？
左10px; 其他都是30px

margin：外边框
border:

border:1px solid #000;
border-width
border-style：solid（实体）,dashed（虚线）,dotted（点）
border-color

行内元素和块级元素

p标签虽然是文本标签，但是它可以当容器来使用，p标签内一定不能放div; p段落也是块元素，他独占一行
文本元素：p span a i em u b strong img
容器级：div li dt dd h级（不建议）
除了p，所有的文本元素，都是行内元素
所有容器级别的元素，都是块元素
块和行内元素的相互转化

display：inline; //行内
display:inline-block;//行内块
display：block; //块

关于定位：大部分情况，建议的是:父相子绝（父亲：相对定位，儿子：绝对定位）
关于脱离文档流的方法
浮动 float:left; float:right;
绝对定位 position:absolute;
固定定位 position:fixed;
重点：1）父相子绝 2）行内元素一点脱离文档流，就可以设置宽高了；
注意：行内元素，一旦脱离文档流，虽然能设置宽高，但是，如果不设置宽的话，会默认跟内容一样宽；而块级元素，如果不设置宽度的话，默认跟父级一样块，没有父级的话，默认跟屏幕一样宽
清除浮动

固定高度height:xxxpx;
缺点：如果作为产品列表的容器展示，我们无法知道容器的具体高度
overflow:hidden
clear:both
缺点：可以解决浮动引起的文档流错乱问题，但是上面浮动元素的父容器该没有高度还没有高度

伪类清除浮动

ul::after{
display: block;
height:0;
content: '';
clear: both;
}

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溢出隐藏
清除浮动
缺点：如果父容器比较小，子容器比较大；父容器如果通过overflow:hidden来清除浮动的话，子容器就看不到了

透明度处理

rgba() 背景透明，文字不透明；

opacity:0 背景透明，文字也透明；

opacity:0.1;/*不兼容IE7浏览器*/
filter:alpha(opacity=10);

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最基本的开发，首先必须创建的项目结构

images文件夹：放切好的图片
css文件夹：放置css文件：index.css
index.html文件

关于继承

宽度继承：如果没有父级，块元素的宽度默认跟可视区一样宽；如果有父级的情况下，默认跟父级宽度一样宽(宽度可以继承，但高度无法继承;)
font可以继承
color可以继承：当遇到a标签的时候， color无效；
line-height可以继承

当文本超度固定宽度的处理方法：

单行文本出超固定宽度出现省略号的写法：
```
white-space:nowrap;
overflow:hidden;
text-overflow:ellipsis
```
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英文不折行的问题处理： word-wrap:break-word;
出现滚动条的写法overflow-y:scroll;

区分伪类和伪元素

伪元素：用:和::都可以，现在建议用::
伪类：给当前选择器添加动效，只能用:

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