Hmm, it appears you can't create a mapping to a directory outside your home directory. I haven't actually done it so I didn't realize. Ok, skip that and delete the mapping you created. Let's try an alternate approach, one I actually prefer, myself.
Log in to your account via SSH and run these commands:
ln -s /usr/share/apache/icons/ icons
(where "www.example.org" is the directory of the site in question).
This is (more-or-less) how I do it on one of my sites. It eliminates the need to remap a directory.
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