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/* 选择所有class里以col开头的元素 */
.row>div{
border: black solid 1px;
background-color: aqua;
height: 50px;
}
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<div class="container">
<div class="row">
<div class="col-lg-3 col-md-4 col-sm-6 col-xs-12">阿嘎是发噶十分的</div>
<div class="col-lg-3 col-md-4 col-sm-6 col-xs-12">发电公司梵蒂冈</div>
<div class="col-lg-3 col-md-4 col-sm-6 col-xs-12">山东分公司梵蒂冈</div>
<div class="col-lg-3 col-md-4 col-sm-6 col-xs-12">山东分fgzfg</div>
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每一个row>div的宽度是row的25%,也就是row分为12列,每个div占3列:
并且div设置了向左浮动left:
如果给div设置margin属性,那么会撑开父元素,脱离文档流
.row>div{
border: black solid 1px;
background-color: aqua;
height: 50px;
margin: 0 10px;
}