The code snippet in post 8 is not a suggestion to be interpreted, it is exactly the code you need to use to hide that link on ez-page 20. You can also adapt it very simply by changing 'page' to whatever page name you want (this is the "main_page=xxx" in the address bar at the top of the window) and eliminating the "or ..." part.
PHP Code:
if ($current_page_base != 'what_ever') {
  <
a href="index.php?main_page=what_ever"><img src="/images/imagename.png" alt="Image Description" width="200" height="50" hspace="5" vspace="5" border="0"></a>

There are other methods to achieve the same result, too.