set class attirbute html code example

Example 1: css class attribute

<h1 class="Class">Content</h1>
<h1 id="id">Content</h1>
Css: 
.class
#id

Example 2: html specific class color

<!-- in the head element -->
<style> h1 { color:blue; } </style>

<!-- in the body element -->
<h1> text in blue because all "h1" element is in blue </h1>