<style type="text/css">
    .a {
        background: transparent none left top no-repeat;
        position: absolute;
        visibility: hidden
    }
</style>
<div class="a" style="background-image: url('heavyimage.jpg')"></div>
<div class="a" style="background-image: url('anotherheavyimage.jpg')"></div>
<div class="a" style="background-image: url('maybesomethingnotsobig.gif)"></div>
<div class="a" style="background-image: url('helloworld.png')"></div>