The tabs as they are now are written in the template. They are not added with the Plugin:AddWebTab() function.
Code:
<li class='active'><a href='./../../../webadmin/Core/Manage_Server'>Manage Server</a></li>
<li><a href='./../../../webadmin/Core/Server_Settings'>Server Settings</a></li>
<li><a href='./../../../webadmin/Core/Chat'>Chat</a></li>
<li><a href='./../../../webadmin/Core/Playerlist'>Playerlist</a></li>
<li><a href='./../../../webadmin/Core/Whitelist'>Whitelist</a></li>
<li><a href='./../../../webadmin/Core/Permissions'>Permissions</a></li>
<li class='last'><a href='./../../../webadmin/Core/Manage_Plugins'>Manage Plugins</a></li>