Have you every wanted to hide ad blocks or some other content in Drupal when you're logged in? To do so, you will need to enter this code block into the "Show if the following PHP code returns TRUE (PHP-mode, experts only)" section under Page specific visibility settings.

<?php
global $user;
if ($user->uid != 1 && $user->uid !=3)
  return TRUE;
?>

The part that you would be concerned with is after the 'if.' The first user create has a uid of 1. I also don't want to show this block to my other user account - uid 3, so I've added it in. If you only want to not display this block for the uid 1 user, the use the following code.

<?php
global $user;
if ($user->uid != 1)
  return TRUE;
?>

I hope you find this helpful!