It seems to be a problem with show/hide in Safari. The site looks good freshly loaded. But if you click on the first link up in the left corner and than go back, the show/hide function doesn't work so well anymore and you get layers on top of each other. Note: This problem only occours in Safari.
I've used jQuery and here is my show hide code:
<script type="text/javascript">
function show(id) {
document.getElementById(id).style.visibility = "visible";
}
function hide(id) {
document.getElementById(id).style.visibility = "hidden";
}
</script>
Link to site: http://www.smudesign2012.co.uk/