I want to get height ( or width.. doesnt really matter ) from `element A` and use that height to set css to `element B` ...like 

```
$('#element_B').css({ 'top','element_A_height' })

```

A little example here.. I know the javascript is not even close to something that works, I just tried to explain what i wanted to happen..

<http://jsfiddle.net/cJdXg/>

I have no idea how to achieve this.. any ideas?