CSS/nth-childを使ったリスト

ul {
	list-style: none;
	margin-top: 30px;
}

ul#sample1 li{ 
  color:white;
  background-color:#555;
  text-align:center;
  display:table-cell;
  line-height:50px; 
  width: 50px;
  height: 50px;
  -webkit-border-radius: 50%;
  -moz-border-radius: 50%;
  border-radius: 50%;
}
ul#sample1 li:nth-child(even){
  background-color:#eee;
  color:black;
}

ul#sample2 li{ 
  color:white;
  background-color:#555;
  text-align:center;
  display:table-cell;
  line-height:50px; 
  width: 50px;
  height: 50px;
  -webkit-border-radius: 50%;
  -moz-border-radius: 50%;
  border-radius: 50%;
}
ul#sample2 li:nth-child(odd){
  background-color:#eee;
  color:black;
}

ul#sample3 li{ 
  color:white;
  background-color:#555;
  text-align:center;
  vertical-align: middle;
  display:table-cell;
  width: 50px;
  height: 50px;
}
ul#sample3 li:nth-child(3n){
  background-color:#eee;
  color:black;
}

ul#sample4 li{ 
  color:white;
  background-color:#555;
  text-align:center;
  vertical-align: middle;
  display:table-cell;
  width: 50px;
  height: 50px;
}
ul#sample4 li:nth-child(n+4){
  background-color:#eee;
  color:black;
}

ul#sample5 li{ 
  color:black;
  background-color:#555;
  text-align:center;
  display:block;
  width: 200px;
  height: 50px;
  border-top: 2px ridge #111;
  border-left: 2px ridge #111;
  border-right: 2px ridge #111;
    }
ul#sample5 li:first-child{
  background-color:#eee;
  color:black;
}
ul#sample5 li:last-child{
  background-color:#eee;
  color:black;
  border-bottom: 2px ridge #ccc;
}