full page background image in html

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-position: center;
3  background-repeat: no-repeat;
4  background-size: contain;
5}

1 I have set the fixed position, you can set it to whatever you want.
2
3.bg-image {
4   width: 100%;
5   height: 100%;
6   position: fixed;
7   right: 0;
8   left: 0;
9   top: 0;
10   bottom: 0;
11 }

1body {
2  background-image: url('img_girl.jpg');
3}