Lists

The two most common types of lists are ordered and unordered.

<ol>
  <li>Apples</li>
  <li>Bananas</li>
  <li>Cherries</li>
</ol>

and

<ul>
  <li>Apples</li>
  <li>Bananas</li>
  <li>Cherries</li>
</ul>

Code Readability

Starting each element on its own line and indenting child elements makes the code much easer to scan at a glance, and also makes it easier to spot missing closing tags.

Would you rather read this:

<body><h1>
Hello! Here are some of my favorite fruits:
</h1>
<ol><li>Apples</li> <li>Bananas</li>
<li>Cherries</li></ol>
</body>

or this:

<body>
  <h1>Hello! Here are some of my favorite fruits:</h1>
  <ol>
    <li>Apples</li>
    <li>Bananas</li>
    <li>Cherries</li>
  </ol>
</body>

I thought so. :-)