Magento client denied by server configuration: /var/www/magento/app/etc/local.xml .. This is not the error, but just a message type thing displayed in apache error log and firebug console. Nothing to worry here, it’s just a security check from web server and you should ignore it.

If you don’t like it then you can turn it off by writing few lines of code in app/design/adminhtml/default/default/layout/local.xml

<layout>  
 <default>  
 <remove name="notification_security"></remove>  
 <remove name="notification_survey"></remove>  
 </default>  
</layout>

Clear cache as usual, and you should get rid of this message.