总结30个CSS3选择器

<ul>
   <li> List Item </li>
   <li> List Item </li>
   <li> List Item </li>
</ul>

ul {
 width: 200px;
 background: #292929;
 color: white;
 list-style: none;
 padding-left: 0;
}
 
li {
 padding: 10px;
 border-bottom: 1px solid black;
 border-top: 1px solid #3c3c3c;
}

div p:only-child {
   color: red;
}

<div><p> My paragraph here. </p></div>
<div>
   <p> Two paragraphs total. </p>
   <p> Two paragraphs total. </p>
</div>

li:only-of-type {
   font-weight: bold;
}

ul > li:only-of-type {
   font-weight: bold;