Sum of cells in a Table
<p>I have a table and I want to add cells together </p>

<pre><code>  &lt;table width="100%" border="0"&gt;
    &lt;tr&gt;
      &lt;td id="a1"&gt;5&lt;/td&gt;
      &lt;td id="a2"&gt;8&lt;/td&gt;
      &lt;td id="a3"&gt;&lt;/td&gt;
    &lt;/tr&gt;
    &lt;tr&gt;
      &lt;td id="b1"&gt;&lt;/td&gt;
      &lt;td id="b2"&gt;&lt;/td&gt;
      &lt;td id="b3"&gt;&lt;/td&gt;
    &lt;/tr&gt;
&lt;/table&gt;
</code></pre>

<p>Lets say I want to add a1 and a2 and display the sum in a3 how could I do that in javascript?</p>
