Make sure that you visit the project page to be sure that you cove all
functionalities.

The user may be able to search through a category structure of the
product catalog or directly through a search function. In principle,
it would be nice if any search results can be firther refined in a
simple way (i.e., the user may select a few on which to see more
details).

If you assume a flexible product cataog structure, then you will have
to show how it is maintained by the administrator.

Any field that is a category (like "type of movie") should be entered
through a menu not through a textbox (to avoid typos).

Look carefully at your page layout (proper selection of widgets, right
number alignment, left string alignment ...) and color scheme
http://www.webdevelopersnotes.com/design/colour_combinations.php3
http://www.colorschemer.com/online.html

Remember to have a footer with links to (a) contact info, (b)
webmaster, (c) privacy statement and such.

Look at http://www-03.ibm.com/easy/page/611 for more interesting
points on the design of an online ecommerce application.

Make sure that you store purchases so that you can potentially do data
mining at the end.

When using images from the web, make sure do not violate copyright laws.

Choose a language and be consistent in your choice and your terminology.

Make sure that you use all technologies we studied:
1) CSS for consistent reusable  look-and-feel of documents
2) JavaScript for client-side interactivity
3) perl for server-side functionality
4) XML for data persistence (and possibly for data exchange beween client and server)