Check out example codes for "how to cover full image in css". It will help you in understanding the concepts better.

Code Example 1

body {
  background-position: center;
  background-repeat: no-repeat;
  background-size: cover;
}

Code Example 2

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

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