Hide random cubes

HTML

<div id="gctu1w_bg" class="bgImage"></div>
<div class="home-animation" id="gctu1w_animation">
    <div class="cube" id="cube_1"></div>
    <div class="cube" id="cube_2"></div>
    <div class="cube" id="cube_3"></div>
    <div class="cube" id="cube_4"></div>
    <div class="cube" id="cube_5"></div>
    <div class="cube" id="cube_6"></div>
    <div class="cube" id="cube_7"></div>
    <div class="cube" id="cube_8"></div>
    <div class="cube" id="cube_9"></div>
    <div class="cube" id="cube_10"></div>
    <div class="cube" id="cube_11"></div>
    <div class="cube" id="cube_12"></div>
    <div class="cube" id="cube_13"></div>
    <div class="cube" id="cube_14"></div>
    <div class="cube" id="cube_15"></div>
    <div class="cube" id="cube_16"></div>
    <div class="cube" id="cube_17"></div>
    <div class="cube" id="cube_18"></div>
    <div class="cube" id="cube_19"></div>
    <div class="cube" id="cube_20"></div>
    <div class="cube" id="cube_21"></div>
    <div class="cube" id="cube_22"></div>
    <div class="cube" id="cube_23"></div>
    <div class="cube" id="cube_24"></div>
    <div class="cube" id="cube_25"></div>
    <div class="cube" id="cube_26"></div>
    <div class="cube" id="cube_27"></div>
    <div class="cube" id="cube_28"></div>
    <div class="cube" id="cube_29"></div>
    <div class="cube" id="cube_30"></div>
    <div class="cube" id="cube_31"></div>
    <div class="cube" id="cube_32"></div>
    <div class="cube" id="cube_33"></div>
    <div class="cube" id="cube_34"></div>
    <div class="cube" id="cube_35"></div>
    <div class="cube" id="cube_36"></div>
    <div class="cube" id="cube_37"></div>
    <div class="cube" id="cube_38"></div>
    <div class="cube" id="cube_39"></div>
    <div class="cube" id="cube_40"></div>
</div>

CSS

.home-animation .cube
{
    background-color: #fff;
    display: block;
    float: left;
    height: 99px;
    margin: 0 1px 1px 0;
    opacity: 0;
    width: 99px;
}
.bgImage, .home-animation
{
    background-position: left top;
    background-repeat: no-repeat;
    height: 400px;
    left: 0;
    margin: 0 auto;
    position: absolute;
    top: 0;
    width: 1000px;
    z-index: -1;
}

.bgImage
{
    display: none;
    background-color: orange;
}

JavaScript

// Translated from scriptaculus 
// http://mobile.bebitalia.com/home.do



$(function() {

    $('.cube').each(function(index, element) {
        var sleepTime = Math.floor(Math.random() * 2000);
        var t = setTimeout(function() {
            var d = Math.floor(Math.random() * 1000);
            $(element).fadeTo(d, 0.99);
        }, sleepTime);
    });

    var h = setTimeout(hideCube, 4000);

});