Any text that looks like a link or an email address should be actionable (i.e., clicking on it should lead to a new page if it is a link or to a mail composing window if it looks like an email address). Consider using maps to show the address of your store.
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 cataolg structure, then you will have to show how it is maintained by the administrator.
Make sure that you do stringent client-side data validation. To that end, any field that takes values from an enumerated set (like "type of movie") should be entered through a alphanumerically ordered menu and not through a textbox (to avoid typos). In addition, javascript functions should be developed to check the value of any field that should have a particular structure.
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 and http://www.colorschemer.com/online.html. make sure that you do not waste too much space with the logo but you have one visible on each page.
Make sure that for each set of data that refer to a different type of information (catalog, shopping cart, news, company information, user-specific information etc) there is a distinguishing characteristic to separate it from the rest of the page (font, background, ...). Remember "things that belong together should look somehoe related either in appearance or in location and things that are separate should appear so).
Think about how your application changes when the user resizes the window or the character set used.
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
Make sure that you use all technologies we studied: