Try this:
<?
$result = do_query("SELECT current_imp FROM account", GameDB);
$imp = mysql_num_rows($result);
echo '<div style="clear:both;margin-top:50px;"><table><tr><td>Total Item Mall Points:</td><td>'. $imp. '</td></tr></table></div>';
?>
You only put "" around the query itself, then tag the database on after the quotes.
I use echo 'stuff'; (the singles quote marks) because I've found it can be tedious to add the backslashes before the "s (double quote marks) in the html. But if I use the singles instead of the doubles, the only time have to add the backslash is if there's a single quote mark, which isn't nearly as often in html code...
Just a tip I found helpful, in case you're interested.