css 下边框

 

 
    float: left;
    width: 1200px;
    height: 42px;
    background-color: #fff0;
    /* background-color: #4f4aff; */
    border-bottom: 1px solid #247fbd; 下边框

margin: 0px 0px 15px 0px; 下边距 15

text-decoration: none; 去掉下划线