SO fiddle

Test Fiddle mainly for SO Questions

HTML

<div id="plane"></div>

CSS

html, body { height:100%; width:100%; margin:0; padding:0; }
#plane { width:100%; height:100%; position:relative; }
.randomnumber { position:absolute; padding:10px; }

JavaScript

$(document).ready(function () {
    var numElems = 500,
        rand = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'];
        
    for(var i = 0; i < numElems; i++) {
        var newElem = document.createElement('div'),
            color = '#' + rand[Math.floor(Math.random() * 15)] + rand[Math.floor(Math.random() * 15)] + rand[Math.floor(Math.random() * 15)] + rand[Math.floor(Math.random() * 15)] + rand[Math.floor(Math.random() * 15)] + rand[Math.floor(Math.random() * 15)];
        newElem.classList.add('randomnumber');
        newElem.innerHTML = i;
        newElem.style.background = color;
        $('#plane').append(newElem);
    }
    $(".randomnumber").each(function () {        
        var randomtop = Math.floor(Math.random() * ($(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
        });
    });
});