CSS/contentプロパティ

#sample1 {
  text-align: left;
  width: 70%;
  margin-top: 70px;
  margin-bottom: 30px;
}
.sampleA:after {
  content: "after";
  font-size: 12px;
  background: #aaa;
  color: #fff;
  padding: 3px 3px 3px 3px;
  margin-left: 5px;
  border-radius: 3px;
}
.sampleB:before {
  content: "before";
  font-size: 12px;
  background: #aaa;
  color: #fff;
  padding: 3px 3px 3px 3px;
  margin-right: 5px;
  border-radius: 3px;
}

#sample2 {
  width: 70%;
  text-align: left;
  margin-top: 30px;
  margin-bottom: 30px;
}
#sample2 li{
  list-style: none;
  counter-increment : number;
}
#sample2 li:before {
  content : "第" counter(number) "項";
  padding-right: 10px;
} 

#sample3 {
    position:relative;
    padding:15px;
    background:#ecf0f1;
    color:#2c3e50;
    font-size:40px;
    text-align:center;
    z-index:2;
    overflow:hidden;
    width: 70%;
    margin-bottom:30px;
    margin-left: 20px;
}
#sample3:before {
    position:absolute;
    top:-25px;
    left:2px;
    content:"sample3";
    display:block;
    color:rgba(000,000,000,0.05);
    font-size: 125px;
    font-weight:bold;
    letter-spacing: 0.1rem;
    line-height:1;
    -webkit-transform:rotate(-10deg);
    -moz-transform:rotate(-10deg);
    transform:rotate(-10deg);
    z-index:-1;
}

#sample4 {
    position:relative;
    padding:15px;
    background:#ecf0f1;
    color:#2c3e50;
    font-size:40px;
    text-align:center;
    z-index:2;
    overflow:hidden;
    width: 70%;
    margin-left: 20px;
}
#sample4:before {
    position:absolute;
    top:-30px;
    left:3rem;
    content: url("../img/@.png")"rise";
    display:block;
    color:rgba(000,000,000,0.25);
    font-size: 25px;
    font-weight:bold;
    letter-spacing: 0.1rem;
    line-height:1;
    -webkit-transform:rotate(-20deg);
    -moz-transform:rotate(-20deg);
    transform:rotate(-20deg);
    z-index:-1;
}

#sample5 {
	margin: 30px;
}
#sample5 a:after {
	content: "["attr(href)"]";
	color: #333;
}

#sample6 {
	margin: 30px;
	padding-bottom:30px;
}
#sample6 ul {
	list-style-type: none;
	margin-top: 0;
}
#sample6 li {
	float: left;
}
#sample6 li + li:before {
	content: ">";
	margin-left: 10px;
	margin-right: 10px;
}