how to make background size flexible in css3 code example

Example 1: how to scale a bg image acc to size of div

/* One way */
background-size: cover;

/* Other option */
background-size: contain;

Example 2: background shrinks when responsive

html,
body {
	width: 100%;
	height: 100%;
	margin: 0px;
	padding: 0px;
	overflow-x: hidden;
}