css background image size to fit screen

1html {
2    height: 100%
3}
4body {
5    background-image:url("../images/myImage.jpg");
6    background-repeat: no-repeat;
7    background-size: 100% 100%;
8}

1html { 
2  background: url(images/bg.jpg) no-repeat 
3    center center fixed; 
4  -webkit-background-size: cover;
5  -moz-background-size: cover;
6  -o-background-size: cover;
7  background-size: cover;
8}

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}

1#example1 {
2  background: url(mountain.jpg);
3  background-repeat: no-repeat;
4  background-size: auto;
5}
6
7#example2 {
8  background: url(mountain.jpg);
9  background-repeat: no-repeat;
10  background-size: 300px 100px;
11}

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

1html {
2    height: 100%;
3}
4body {
5    color: #999;
6    background: url('../images/background/main_bg.jpg') no-repeat center center fixed;
7    font-family: 'Roboto', sans-serif;
8    -webkit-background-size: cover;
9    -moz-background-size: cover;
10    -o-background-size: cover;
11    background-size: cover;
12}