Here is your code in a jsfiddle example. I have tested it and it looks fine.
http://jsfiddle.net/dimshik/9DbEP/4/
I used a simple table, maybe you are missing some CSS on your new page that was created with JavaScript.
<table border="1" cellpadding="3" id="printTable">
<tbody><tr>
<th>First Name</th>
<th>Last Name</th>
<th>Points</th>
</tr>
<tr>
<td>Jill</td>
<td>Smith</td>
<td>50</td>
</tr>
<tr>
<td>Eve</td>
<td>Jackson</td>
<td>94</td>
</tr>
<tr>
<td>John</td>
<td>Doe</td>
<td>80</td>
</tr>
<tr>
<td>Adam</td>
<td>Johnson</td>
<td>67</td>
</tr>
</tbody></table>