Ok, here it is: posted and attached (in case the post looks like crap). You see I break out of php to do the html. Even within a loop, this will still work, and it will produce nice, easy to read rendered source code. We had a thread about this a while ago that dalecosp started, and at the time, I never did this sort of thing. Since then, I've become a real stickler with how my rendered code looks, mainly for this reason of debugging. Plus, I'm just an anal bastard. Hope this helps give you some ideas. Also, I removed you're comments so mine would stick out to you.
<?php
require_once("../../../includes/configs/config.cfg");
require_once("../../../includes/configs/select_db.cfg");
## require_once allows it to be called later without error
$show=$_GET['show_cat'];
$sql = "SELECT *
FROM `poster`
WHERE category=".$show."
ORDER BY 'code' ASC";
## I prefer to break out of strings with "." when calling a variable
$results = mysql_query($sql) or die(mysql_error());
## mysql_error will give a more detailed error of the problem
while($results_row = mysql_fetch_array($results)) {
extract($results_row);
?>
<table cellspacing="5" cellpadding="0" border="0" width="100%">
<tr>
<td align="left" valign="top" width="35"><a href="full_view.php?show_cat=<?php echo $results_row['ID']; ?>">
<br /><img src=../../../images/<?php echo $results_row['imagethumb']; ?>"></a>
</td>
<td align="left" valign="top" height="167">
<table cellpadding="2" cellspacing="0" border="0" height="136" width="100%">
<tr>
<td><div class=unnamed1><a href="full_view.php?show_cat=<?php echo $results_row['ID']; ?>"><?php echo $results_row['code']; ?></a></td>
</tr>
<tr>
<td bgcolor="#eaeaea"><div class="unnamed1"><font color="#000000"><?php echo $results_row['postername']; ?></font></div></td>
</tr>
<?php
$artist_id=$results_row['artist'];
$artist_sql = "SELECT *
FROM `artist`
WHERE ID=".$artist;
$artist_results = mysql_query($artist_sql) or die(mysql_error());
while($artist_row = mysql_fetch_array($artist_results)) {
extract($artist_row);
?>
<tr>
<td><div class="unnamed1"><?php echo $artist_row['artistname']." ".$artist_row['artistlastname']; ?></div></td>
</tr>
<tr>
<td><div class="unnamed1">Paper Size:</div></td>
</tr>
<tr>
<td><div class="unnamed1"><?php echo $results_row['papersizeincheswt']." x "
.$results_row['papersizeinchesht']." In | "
.$results_row['papersizecmwt']." x "
.$results_row['papersizecmht']." Cm"; ?>
</div>
</td>
</tr>
<tr>
<td><div class="unnamed1">Image Size:</div></td>
</tr>
<tr>
<td><div class="unnamed1"><?php echo $results_row['imagesizeincheswt']." x "
.$results_row['imagesizeinchesht']." In | "
.$results_row['imagesizecmwt']." x "
.$results_row['imagesizecmht']." Cm"; ?>
</div>
</td>
</tr>
<tr>
<td><div class="unnamed1">$<?php echo $results_row['price']; ?></div></td>
</tr>
</table>
</td>
</tr>
</table>"
<?php
}
}
?>