Как вариант...
<!DOCTYPE html>
<html>
<head>
<title>test</title>
<style type="text/css">
</style>
<script type="text/javascript">
function Go() {
var o=document.getElementById('div-spasibo-torrent')
if (o.parentNode.id=='contentBlock') alert('Ok')
}
</script>
</head>
<body onload='Go()'>
<div id='contentBlock'>
<div id='div-spasibo-torrent'></div>
</div>
</body>
</html>