清浮动的三种方法

.warp{
    width:1260px;
    margin:auto;
    border:1px solid red;
}
clo{
    width:80%;
    height:100px;
    float:left;
    background-color:#e34cf1;
    border:5px solid #fff;
}

<div id="wrap2" class="warp">
    <div id="one" class="clo" ></div>
    <div id="two" class="clo"></div>
    <div id="three" class="clo"></div>
    <div id="four" class="clo"></div> 
</div>

#wrap2{
    border:2px solid green;
    overflow:hidden;
}

<div id="wrap3" class="warp">
    <div id="one" class="clo" ></div>
    <div id="two" class="clo"></div>
    <div id="three" class="clo"></div>
    <div id="four" class="clo"></div> 
</div>

#wrap3:after{
    content:" ";
    display:block;
    height:0px;
    clear:both;
}