.image{
    height:100px;
    width:100px;
    background-image: url(cat.gif);background-repeat:no-repeat;background-position:center;
    position:fixed;
}
.bigbox{
    height:300px;
    width:300px;
    background-color:cornflowerblue;padding-top:1px;
    position:relative:left:30%;
}
.littlebox{
    height:100px;
    width:100px;
    border-radius:50px;
    background-color:crimson;
}
html{
    background:
        url(cat.gif) no-repeat center fixed;
    -webkit-background-size:cover;
    -moz-background-size:cover;
    background-size:cover;
}
html{
    background:
        url(frog.gif)no-repeat center center fixed;
    -webkit-background-size:cover;
    -moz-background-size:cover;
    -o-background-size:cover;
    background-size:cover;
}
@media screen and (min-width:800px){
    .class{
        }
    .littlebox{
        height:50px;
        width:50px;
        border-radius:50px;
        background-color:yellowgreen;
    }
}