border-bottom:1px dotted 虚线
.content .list ul li:nth-child(5n+1){
margin-left: 0;
}
.content .list ul li:nth-child(5n){
margin-right: 0;
}
background-image: url(../img/icon/ico.png);
height: 12px;
width: 12px;
display: inline-block;
background-repeat: no-repeat;
background-position: 0px -71px;
margin-left:10px; 精灵图