There are a lot or warnings with your theme - 428 to be precise.
Most of it is coming from the badly scripted "BoardNews" - And some you have created yourself.
The script below needs "tables" as you can't have <tr><td> inside <div's>
div's need to be either outside of a table, or inside the <td>
Anyway - here's one that you should fix up?
<div id="bg">
<--- Start table here --->
<tr>
<td width="100%" colspan="3" valign="top">
<div id="top_logo">
<table class="" width="100%" cellspacing="0" cellpadding="0" border="0">
<tr>
<td align="left" height="100%" valign="middle">
<div id="logo-img"><a href="http://www.hellomotorazrforum.com/index.php" title="Home"><img src="http://www.hellomotorazrforum.com/templates/hmr/images/dark_force/sitelogo_small.png" alt="Home" title="Home" /></a></div>
</td>
<td align="center" valign="middle"> </td>
<td align="right" valign="middle">
<!-- <div class="sitedes"><h1>Mobile Modding Community</h1></div> -->
</td>
</tr>
</table>
</div>
</td>
</tr>
<--- Finish table here --->
</div>
And another one.
<th width="180"><ul class="lastpost"> Last Post </ul></th>
If you are going to use <ul> like you have here:
(Though I have no idea why you can't pass that to the <th class=" etc, or at most use a <span class="etc)
With <ul's> you need to make it like this: <ul class="lastpost"><li> Last Post </li></ul>
You may even have to give the line a class, depending on what you are trying to do?
That should fix some of the problems -
Only 424 to go!