When somebody says "clean up code" it probably means that the code is a mess and there are a lot of tags that aren't really doing anything. Example:
Originally Posted by LAMA
This is obviously a bad example, but bear with me.
<table width="100%" border="0" cellpadding="10" cellspacing="0">
<font face="Verdana"><font size="3"><font color="red"><b>Hello</b></font></font></font>
That code above can easily be translated into something like this:
There is far less code in the second example than in the first even though they both give the same effect. Doing this will make your file size that much smaller. Smaller file sizes = faster loading pages.
<div style="padding: 10px; font: bold 15px Verdana, Arial, Helvetica, sans-serif; color: red;">Hello</div>