non stai applicando il codice correttamente

copia e incolla l'esempio

codice:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html>
<head>

<script type="text/javascript">
function apri(link){
var elemento= document.getElementById("layer1");
elemento.innerHTML = link.innerHTML;
elemento.style.display="block";
return false;
}
</script>
</head>


<body>
Prima fase

Seconda fase

Terza fase</script>

<div id="layer1" style="position:absolute; border:1px solid #000000; width:200px; height:40px; top:300px; left:150px; z-index:1; display:none"></div>


</body>
</html>