Вкрно понимаете, и нет, там всё взаимосвязано.
<div id="myDiv">
aaaaaaaa<br />aaaaaaaaaaaaa<br />
aaaaaaaa<br />aaaaaaaaaaaaa<br />
aaaaaaaa<br />aaaaaaaaaaaaa<br />
aaaaaaaa<br />aaaaaaaaaaaaa<br />
aaaaaaaa<br />aaaaaaaaaaaaa<br />
aaaaaaaa<br />aaaaaaaaaaaaa<br />
aaaaaaaa<br />aaaaaaaaaaaaa<br />
aaaaaaaa<br />aaaaaaaaaaaaa<br />
</div>
<script type='text/javascript'>
alert(document.getElementById('myDiv').offsetHeight);
</script>