SO fiddle

Test Fiddle mainly for SO Questions

HTML

<div id="plane">
    <div class="randomnumber aaa">1</div>
    <div class="randomnumber bbb">2</div>
    <div class="randomnumber ccc">3</div>
    <div class="randomnumber ddd">4</div>
    <div class="randomnumber eee">5</div>
    <div class="randomnumber fff">6</div>
    <div class="randomnumber ggg">7</div>
    <div class="randomnumber hhh">8</div>
    <div class="randomnumber iii">9</div>
    <div class="randomnumber jjj">0</div>
</div>

CSS

html, body { height:100%; width:100%; }
#plane {
    width:100%; height:100%;
    position:relative;
}
.randomnumber { position:absolute; padding:10px; }
.aaa {background:#a10;}
.bbb {background:#b1b;}
.ccc {background:#1cc;}
.ddd {background:#ddf;}
.eee {background:#ef0;}
.fff {background:#f0f;}
.ggg {background:#dfe;}
.hhh {background:#e1e1e1;}
.iii {background:#f00;}
.jjj {background:#0ff;}

JavaScript

$(document).ready(function () {
    $(".randomnumber").each(function () {
        var randomtop = Math.floor(Math.random() * ($(window).height() - $(this).height() - 20)),
            randomleft = Math.floor(Math.random() * ($(window).width() - $(this).width() - 20)),
            randomzindex = Math.floor(Math.random() * 30);
        $(this).css({
            "top": randomtop,
            "left": randomleft,
            "z-index": randomzindex
        });
    });
});