When attempting to add an item to the shopping cart, the item is not added and I am sure the page is designed correctly.

You should design a simple cartitadd page for testing to make 100% sure your page design is OK.

<FORM ACTION="/cgi-bin/cartit.cgi" METHOD="POST"> -or cartit.exe if using CartIt NT
<INPUT TYPE="HIDDEN" NAME="cartitadd" VALUE="Test Product^19.95^1">
<INPUT TYPE="SUBMIT" VALUE="Add Item to Shopping Cart!">

If this continues to fail, then the reason is most likely that you have your "Spoof Control" features set incorrectly

In CartIt NT you can correct this from the CartIt Manager URL.

In CartIt for UNIX you can do this from CommerceBuddy under Options -> Advanced Spoof Control.

Click the "Click Here for Suggested Expression" link. If your CommerceBuddy is registered, then CommerceBuddy will create an expression for you to use (you should see your domain name in the espression). Do not change the suggested expression unless you are sure of the results.

Be sure you "Publish Options and Configurations" after you make these changes.