(function makeDiv(){
var divsize = ((Math.random()*100) + 50).toFixed();
var color = '#'+ Math.round(0xffffff * Math.random()).toString(16);
$newdiv = $('<div/>').css({
    'width':divsize+'px',
    'height':divsize+'px',
    'background-color': color
});

var posx = (Math.random() * ($(document).width() - divsize)).toFixed();
var posy = (Math.random() * ($(document).height() - divsize)).toFixed();

$newdiv.css({
    'position':'absolute',
    'left':posx+'px',
    'top':posy+'px',
    'display':'none'
}).appendTo( 'body' ).fadeIn(100).delay(300).fadeOut(200, function(){
   $(this).remove();
   makeDiv();
});