Check out example codes for "css background image size fit screen". It will help you in understanding the concepts better.

Code Example 1

html { 
  background: url(images/bg.jpg) no-repeat center center fixed; 
  -webkit-background-size: cover;
  -moz-background-size: cover;
  -o-background-size: cover;
  background-size: cover;
}

Code Example 2

<head>
<style>
#example1{
  border: 2px solid black;
  padding: 100px;
  background: url(mountain.jpg);
  background-repeat: no-repeat;
  background-size: 100% 100%;
}
</style>
</head>
<body>
<div id="example1">
</div>
</body>

Code Example 3

-moz-backface-visibility: hidden;

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