What elements can I add a class to? code example

Example 1: javascript add class to element

var someElement= document.getElementById("myElement");
    someElement.className += " newclass";//add "newclass" to element (space in front is important)

Example 2: html create class

<h1 class="write a name">H1 content</h1>

Example 3: html classes

<p class="ClassExample">ClassExample!!</p>