css布局

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左右布局

If two elements are displayed as a block:
html structure

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<div class="wrapper clearFix">
<div class="red"></div>
<div class="blue"></div>
</div>

float方法

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css:
.clearFix:after{
display:block;
content:'';
clear:both;
}

.red{
width: 100px;
height: 50px;
background: red;
float:left;
}

.blue{
width: 100px;
height: 50px;
background: blue;
float:left;
}

flex布局

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.wrapper{
display:flex;
flex-direction:row;

}
.red{
width: 100px;
height: 50px;
background: red;
}

.blue{
width: 100px;
height: 50px;
background: blue;
}

If two elements are displayed as an inline element:

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.red{
width: 100px;
height: 50px;
display:inline-block;
background: red;
}

.blue{
width: 100px;
height: 50px;
display:inline-block;
background: blue;
}

左中右布局

html structure

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<div class="wrapper clearFix">
<div class="red"></div>
<div class="blue"></div>
<div class="yellow"></div>
</div>

If two elements are displayed as a block:

float方法

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.clearFix:after{
display:block;
content:'';
clear:both;
}

.red{
width: 100px;
height: 50px;
background: red;
float:left;
}

.blue{
width: 100px;
height: 50px;
background: blue;
float:left;
}

.yellow{
width: 100px;
height: 50px;
background: yellow;
float:left;
}

flex布局

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.wrapper{
display:flex;
flex-direction:row;

}
.red{
width: 100px;
height: 50px;
background: red;
}

.blue{
width: 100px;
height: 50px;
background: blue;
}

.yellow{
width: 100px;
height: 50px;
background: yellow;
}

If two elements are displayed as a inline-element:

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.red{
width: 100px;
height: 50px;
display:inline-block;
background: red;
}

.blue{
width: 100px;
height: 50px;
display:inline-block;
background: blue;
}

.yellow{
width: 100px;
height: 50px;
display:inline-block;
background: yellow;
}

水平居中

inline元素的父元素上设置text-align:center;

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.wrapper{
text-align:center;
}
.red{
width: 100px;
height: 50px;
display:inline-block;
background: red;
}

div+css左右margin为auto(前提：已设置div的宽度)

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.wrapper{
max-width:960px;
}
.red{
width: 100px;
height: 50px;
background: red;
margin:0 auto;
}

绝对定位和margin-left：-(width/2);left:50%;

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.wrapper{
position: relative;
}
.red{
width: 100px;
height: 50px;
background: red;
position: absolute;
left:50%;
margin-left:-50px;
}

flex布局

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.wrapper{
display:flex;
flex-direction:column;
}
.red{
width: 100px;
height: 50px;
background: red;
align-self:center;
}

或者

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.wrapper{
display:flex;
flex-direction:column;
}
.red{
width: 100px;
height: 50px;
background: red;
margin:0 auto;
}

垂直居中

绝对定位和margin-top：-(height/2);top:50%;

缺点：需要事先知道div的尺寸（高度）

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.wrapper{
width:100%;
height:300px;
position: relative;
background:#fff;
}
.red{
width: 50%;
height: 150px;
background: red;
position: absolute;
top:50%;
margin-top:-75px;
}

绝对定位和margin:auto;

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.wrapper{
width:100%;
height:300px;
position: relative;
background:#fff;
}
.red{
width: 50%;
height: 150px;
background: red;
position: absolute;
top:0;
bottom: 0;
margin:auto;
}

flex布局

注意：flex-direction默认属性是row

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.wrapper{
width:100%;
height:300px;
display:flex;
background:#fff;
align-items:center;
flex-direction:row;
}
.red{
width: 50%;
height: 150px;
background: red;
}

inline元素line-height=元素高度

此方法在inline-height较大时有bug

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html structure:
<div class="wrapper clearFix">
<div class="red">123</div>

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.wrapper{
width:100%;
height:300px;
display:inline-block;
background:#fff;
line-height:300px;
}
.red{
width: 50%;
height: 150px;
background: red;
display:inline-block;
line-height:150px;
}

其他小技巧

画三角形

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.triangle1{
border:10px solid red;
width: 0;
height: auto;
border-top-color:transparent;
border-right-color:transparent;
border-left-color:transparent;
}
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.triangle2{
border:10px solid red;
width: 0;
height: auto;
border-top:0;
border-right-color:transparent;
border-bottom-color:transparent;
}