how to make an image occupy entire page css

1img.bg {
2  /* Set rules to fill background */
3  min-height: 100%;
4  min-width: 1024px;
5	
6  /* Set up proportionate scaling */
7  width: 100%;
8  height: auto;
9	
10  /* Set up positioning */
11  position: fixed;
12  top: 0;
13  left: 0;
14}
15
16@media screen and (max-width: 1024px) { /* Specific to this particular image */
17  img.bg {
18    left: 50%;
19    margin-left: -512px;   /* 50% */
20  }
21}