how to give style to button in html code example

Example 1: button style css

<a class="pure-button pure-button-primary" href="#">A Primary Button</a>
<button class="pure-button pure-button-primary">A Primary Button</button>

Example 2: button style css

<button class="pure-button pure-button-disabled">A Disabled Button</button>
<button class="pure-button" disabled="">A Disabled Button</button>