how to cover full image in css

1html { 
2  background: url(images/bg.jpg) no-repeat center center fixed; 
3  -webkit-background-size: cover;
4  -moz-background-size: cover;
5  -o-background-size: cover;
6  background-size: cover;
7}

1body {
2  background-position: center;
3  background-repeat: no-repeat;
4  background-size: cover;
5}

1body { 
2  background: url(path/to/bg-image.jpg) no-repeat center center fixed;
3  background-size: cover;
4}

1.wrapper{background: url('/assets/64531/green_suburb.jpg') no-repeat   center center fixed;
2-webkit-background-size: cover;
3-moz-background-size: cover;
4-o-background-size: cover;
5background-size: cover;}