Answers for "how does a background image take its full height in css"

how to set background image 100 height

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;
}

make background image full width

html {
    height: 100%;
}
body {
    color: #999;
    background: url('../images/background/main_bg.jpg') no-repeat center center fixed;
    font-family: 'Roboto', sans-serif;
    -webkit-background-size: cover;
    -moz-background-size: cover;
    -o-background-size: cover;
    background-size: cover;
}