El método focus no es aplicable a elementos div a menos que sean de contenido editable (atributo contenteditable="true"). Lo que podés hacer es seleccionar el contenido de la capa:
Código:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<title>test</title>
<script>
function seleccionar(obj){
if(obj.nodeName.toLowerCase()=='textarea' || (obj.nodeName.toLowerCase()=='input' && obj.type=='text')){
obj.select();
return;
}
if (window.getSelection) {
var sel = window.getSelection();
var range = document.createRange();
range.selectNodeContents(obj);
sel.removeAllRanges();
sel.addRange(range);
}
else if (document.selection) {
document.selection.empty();
var range = document.body.createTextRange();
range.moveToElementText(obj);
range.select();
}
}
onload=function(){
seleccionar(document.getElementById('pp'));
}
</script>
</head>
<body>
<div >jjjjj</div>
<div id="pp">jjjjj</div>
<div >jjjjj</div>
<div>jjjjj</div>
</body>
</html>