左边固定宽度右边自适应的三种方法

<div class="both">
    <div class="left"></div>
    <div class="right"></div>
</div>

一、用flex

.both{
    height:500px;
    display:flex;
    flex-direction: row;
}
.left{
    background:red;
    width:200px;
}
.right{
    flex:1;
    background:blue;
}

二、float

.both{
    height:500px;
    overflow:auto;
    *zoom:1;
}
.left{
    background:red;
    width:200px;
    float:left;
    height:100%;
}
.right{
    margin-left:200px;
    background:blue;
    height:100%;
}

三、定位

.both{
    height:500px;
    position:relative;

}
.left{
    background:red;
    position:absolute;
    width:200px;
    left:0;
    height:100%;
}
.right{
    background:blue;
    margin-left:200px;
    height:100%;
}