ok for example here is the url for the DNN download image link. http://www.dotnetnuke.com/tabid/125/default.aspx Note the key piece /tabid/125 the rest of the url is really just basic stuff. The tabid/125 is the key, everything is stored in the Database for DNN and the tabid/125 points the page to the correct information in the database.
Now look at the Directory links url: http://www.dotnetnuke.com/tabid/702/Default.aspx Notice how it has the same format but with /tabid/702/ Thusly its tabid is 702.
Now for the table: Here is the html used by the DNN site for their navigation menu with the icons:
<td valign="top" align="left" id="DNN_HeaderRightBottom">
<!-- Begin Header Actions Table -->
<table height="100%" cellspacing="0" cellpadding="2" border="0" id="DNN_HeaderActions">
<tbody><tr>
<td width="51" valign="bottom" align="center" class="DNN_HeaderActionCell"><a href="http://www.dotnetnuke.com/tabid/125/default.aspx"><img width="46" vspace="3" height="44" border="0" alt="Downloads" onmouseout="this.src='/Portals/_default/Skins/DNN-Minimal//images/icon_downloads.gif'" onmouseover="this.src='/Portals/_default/Skins/DNN-Minimal//images/icon_downloads_over.gif'" src="/Portals/_default/Skins/DNN-Minimal/images/icon_downloads.gif"/></a>
<a class="DNN_IconLink" href="http://www.dotnetnuke.com/tabid/125/default.aspx">Downloads</a>
</td>
<td width="51" valign="bottom" align="center" class="DNN_HeaderActionCell"><a href="http://www.dotnetnuke.com/tabid/702/Default.aspx"><img width="46" vspace="3" height="36" border="0" alt="Directory" onmouseout="this.src='/Portals/_default/Skins/DNN-Minimal//images/icon_directory.gif'" onmouseover="this.src='/Portals/_default/Skins/DNN-Minimal//images/icon_directory_over.gif'" src="/Portals/_default/Skins/DNN-Minimal//images/icon_directory.gif"/></a>
<a class="DNN_IconLink" href="http://www.dotnetnuke.com/tabid/702/Default.aspx">Directory</a>
</td>
<td width="51" valign="bottom" align="center" class="DNN_HeaderActionCell"><a href="http://www.dotnetnuke.com/tabid/795/Default.aspx"><img width="51" vspace="3" height="39" border="0" alt="Forums" onmouseout="this.src='/Portals/_default/Skins/DNN-Minimal//images/icon_forums.gif'" onmouseover="this.src='/Portals/_default/Skins/DNN-Minimal//images/icon_forums_over.gif'" src="/Portals/_default/Skins/DNN-Minimal//images/icon_forums.gif"/></a>
<a class="DNN_IconLink" href="http://www.dotnetnuke.com/tabid/795/Default.aspx">Forums</a>
</td>
<td width="51" valign="bottom" align="center" class="DNN_HeaderActionCell"><a href="http://www.dotnetnuke.com/tabid/824/default.aspx"><img width="37" vspace="3" height="40" border="0" alt="Forge" onmouseout="this.src='/Portals/_default/Skins/DNN-Minimal//images/icon_modules.gif'" onmouseover="this.src='/Portals/_default/Skins/DNN-Minimal//images/icon_modules_over.gif'" src="/Portals/_default/Skins/DNN-Minimal/images/icon_modules.gif"/></a>
<a class="DNN_IconLink" href="http://www.dotnetnuke.com/tabid/824/default.aspx">Forge</a>
</td>
<td width="51" valign="bottom" align="center" class="DNN_HeaderActionCell"><a href="http://www.dotnetnuke.com/tabid/825/default.aspx"><img width="45" vspace="3" height="36" border="0" alt="Blogs" onmouseout="this.src='/Portals/_default/Skins/DNN-Minimal//images/icon_blogs.gif'" onmouseover="this.src='/Portals/_default/Skins/DNN-Minimal//images/icon_blogs_over.gif'" src="/Portals/_default/Skins/DNN-Minimal//images/icon_blogs.gif"/></a>
<a class="DNN_IconLink" href="http://www.dotnetnuke.com/tabid/825/default.aspx">Blogs</a>
</td>
<td> </td>
<td width="51" valign="bottom" align="center" class="DNN_HeaderActionCell"><a href="http://marketplace.dotnetnuke.com"><img width="48" vspace="3" height="43" border="0" alt="Marketplace" onmouseout="this.src='/Portals/_default/Skins/DNN-Minimal//images/icon_mp.gif'" onmouseover="this.src='/Portals/_default/Skins/DNN-Minimal//images/icon_mp_over.gif'" src="/Portals/_default/Skins/DNN-Minimal/images/icon_mp.gif"/></a>
<a class="DNN_IconLink" href="http://marketplace.dotnetnuke.com">Marketplace</a>
</td>
<td width="47" valign="bottom" align="center" class="DNN_HeaderActionCell"><a href="http://www.dotnetnuke.com/tabid/1111/default.aspx"><img width="44" vspace="3" height="43" border="0" alt="Careers Program" onmouseout="this.src='/Portals/_default/Skins/DNN-Minimal//images/icon_careers.gif'" onmouseover="this.src='/Portals/_default/Skins/DNN-Minimal//images/icon_careers_over.gif'" src="/Portals/_default/Skins/DNN-Minimal/images/icon_careers.gif"/></a>
<a class="DNN_IconLink" href="http://www.dotnetnuke.com/tabid/1111/default.aspx">Careers</a>
</td>
</tr>
</tbody></table>
<!-- End Header Actions Table -->
</td>
Notice how they just call different images for onmouseover and onmouseout.
All they are doing are swaping the images when you mouse over to one that looks filled in a bit.