css image to cover full screen code example
Example 1: full page background image
html {
background: url(images/bg.jpg) no-repeat center center fixed;
-webkit-background-size: cover;
-moz-background-size: cover;
-o-background-size: cover;
background-size: cover;
}
Example 2: html background image fit to screen
body {
background-position: center;
background-repeat: no-repeat;
background-size: contain;
}