snow css

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#snow{
        background: none;
        font-family: Androgyne;
        background-image: url('http://www.wearewebstars.dk/codepen/img/s1.png'), url('http://www.wearewebstars.dk/codepen/img//s2.png'), url('http://www.wearewebstars.dk/codepen/img//s3.png');
        height: 100%;
        left: 0;
        position: absolute;
        top: 0;
        width: 100%;
        z-index:1;
        -webkit-animation: snow 10s linear infinite;
        -moz-animation: snow 10s linear infinite;
        -ms-animation: snow 10s linear infinite;
        animation: snow 10s linear infinite;
}
@keyframes snow {
  0% {background-position: 0px 0px, 0px 0px, 0px 0px;}
  50% {background-position: 500px 500px, 100px 200px, -100px 150px;}
  100% {background-position: 500px 1000px, 200px 400px, -100px 300px;}
}
@-moz-keyframes snow {
  0% {background-position: 0px 0px, 0px 0px, 0px 0px;}
  50% {background-position: 500px 500px, 100px 200px, -100px 150px;}
  100% {background-position: 400px 1000px, 200px 400px, 100px 300px;}
}
@-webkit-keyframes snow {
  0% {background-position: 0px 0px, 0px 0px, 0px 0px;}
  50% {background-position: 500px 500px, 100px 200px, -100px 150px;}
  100% {background-position: 500px 1000px, 200px 400px, -100px 300px;}
}
@-ms-keyframes snow {
  0% {background-position: 0px 0px, 0px 0px, 0px 0px;}
  50% {background-position: 500px 500px, 100px 200px, -100px 150px;}
  100% {background-position: 500px 1000px, 200px 400px, -100px 300px;}
}       

<div id="snow">
</div>