[css] CSS background image to fit height, width should auto-scale in proportion

body.bg {
    background-size: cover;
    background-repeat: no-repeat;
    min-height: 100vh;
    background: white url(../images/bg-404.jpg) center center no-repeat;
    -webkit-background-size: cover;
    -moz-background-size: cover;
    -o-background-size: cover;
}   
Try This
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    body.bg {_x000D_
     background-size: cover;_x000D_
     background-repeat: no-repeat;_x000D_
     min-height: 100vh;_x000D_
     background: white url(http://lorempixel.com/output/city-q-c-1920-1080-7.jpg) center center no-repeat;_x000D_
     -webkit-background-size: cover;_x000D_
     -moz-background-size: cover;_x000D_
     -o-background-size: cover;_x000D_
    } 
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    <body class="bg">_x000D_
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    </body>
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