Modify your HTML like this:
<table border="0" cellpadding="0" cellspacing="0">
<thead>
<tr><td>1</td><td>2</td><td>3</td></tr>
</thead>
<tbody>
<tr><td>a</td><td>b></td><td>c</td></tr>
<tr class='odd'><td>x</td><td>y</td><td>z</td></tr>
</tbody>
</table>
(I added border="0" cellpadding="0" cellspacing="0"
)
In CSS, you could do the following:
table {
border-collapse: collapse;
}