Line break above banner

I have a Google ads banner running on the bottom my website betterelectricity.com.au (right below Previous post).

I would like to add a white space (line break) between the words Previous Post and the banner.

I have tried this in my main css but it doesnt work:

#div-gpt-ad-1441077375543-0 {
  margin-top: 100px;
}

Any tips?

The code for the banner is:

<center>
<!-- /64099540/betterelec_ros_lbr_btf -->
<div id='div-gpt-ad-1441077375543-0' style='height:90px; width:728px'>
<script type='text/javascript'>
googletag.cmd.push(function() { googletag.display('div-gpt-ad-1441077375543-0'); });
</script>
</div>
</script>
</div>
</center>