Edit in JSFiddle

<html>
<head>
<title>setting image background with css </title>
</head>

<body>

<h1>Image background</h1>

<p>There is an image behind this text. </p>

</body>

</html> 

body
{
    background-image:url(http://www.hdwallpapers.in/walls/cosmea_floral_bloom-wide.jpg);
}