OK, a few questions:

1 - what's the difference between http://www.youpal.gr/, http://www.youpal.gr/index.php and http://www.youpal.gr/youpal-network  ? Are they all equivalent to the front page?
2 - do you want the module excluded from all of these?
3 - can you please assign a MetaMod to your site, and have it available on all pages. Turn on Advanced Debug, so that we can see the URL parameters that we can use to identify the pages. This will help on SimGallery, too.
4 - perhaps you could add some more galleries or pictures in the gallery, so that you can see the difference between the different pages and categories when you're viewing them.
5 - since I need a login to see the galleries... could you please send me a user account? Thanks!

Cheers,
Stephen

Oh, advanced debug mode makes this so easy :-) Thanks for switching that on.

For the front page(s) you can use this:

if (
  $option != 'com_community'
  or $view != 'frontpage'
  or $Itemid != '161'
) return 153;

That will only place module 153 onto any pages that are *not* the front page.
Please read through the Quick Start guide on http://www.metamodpro.com/get-started/quick-start if you haven't already done so.

For the simgallery, the Advanced Debug is not showing, but based on the URL I think you can identify when you are in that component like this:

if ( $option == "com_simgallery" ) return XXX;

or show a module on every page that isn't inside simgallery:

if ( $option != "com_simgallery" ) return XXX;


Is that what you are after?