Modifying CSS for existing HTML

CSS for dummies help needed

[spinnaker]

Below is a snippet of soem HTML. I would like to change the CSS file to put a blue border with a whit background on the row that says:

<td class="contentheading" width="100%">
<a href="index.php?option=com_content&amp;task=view&amp;id=12&amp;Itemid=47"
class="contentpagetitle">July 18-22 Youth Sailing Camp</a>
</td>

What would I change or add to my CSS file to do that?

<div class="componentheading">
 Events and Seminars
 </div>
 <table class="blog" cellpadding="0" cellspacing="0">
 <tr>
 <td valign="top">
  <br>
  <br>
 </td>
 </tr>
 <tr>
 <td valign="top">
  <div>
  <table class="contentpaneopen">
  <tr>
  <td class="contentheading" width="100%">
   <a href="index.php?option=com_content&amp;task=view&amp;id=12&amp;Itemid=47"
   class="contentpagetitle">July 18-22 Youth Sailing Camp</a> 
  </td>
  </tr>
  </table>
  <table class="contentpaneopen">
  <tr>
  <td valign="top" colspan="2">
   <p>
   <strong>A sub heading</strong><br>
   Just some text.
   </p>
  </td>
  </tr>
  </table>
  </div>
 </td>
 </tr>
 </table>

[abbeyvet]

td.contentheading {background-color:#fff;border:1px solid #369;}

[spinnaker]

Thanks for the quick response. That worked great! Is there anyway to set it only it it is within a blog class table?