can't see the subdirectory image on the left side of the main page

Hi patrik;

Thanks for the wonderful software.
Now i'm using the phpalbum, but I encounter one problem. that is, in your demo, we can find several thumbnails(i think those are the pictures from the subdirectories) on the left side of the main page,but why can't i see these on my page.
Do I have to make any changes?

http://lib.tngs.tn.edu.tw/album

thanks for help.

donald