In header.php look for this code near the bottom:
<?php wp_list_pages('sort_column=menu_order&depth=1&title_li='); ?>
<?php wp_register('<li class="admintab">','</li>'); ?>
</ul>
The wp_register line/call is the "site admin" tab you see when logged in.
Now if you really want the tabs gone, remove the code or comment it out.
However, if like me, you just want certain pages listed in the header tabs, then simply modify the code like so:
<?php wp_list_pages('exclude=2,8,9,10,11,13,15&sort_column=menu_order&depth=1&title_li='); ?>
<?php wp_register('<li class="admintab">','</li>'); ?>
</ul>
The excludes are the page id numbers you want excluded. You can have as few or as many as you like.