Open the 
Contact Card
window: Browse to the relevant contact person card.
Click Functions, Commerce Portal, Remove from Web Portal.
Sometimes you may want to disable your Web portal user's Commerce Portal access. You can delete their Commerce Portal login ID and password by following this procedure:
Open the Contact Card
window: Browse to the relevant contact person card.
Click Functions, Commerce Portal, Remove from Web Portal.
Note
It is not possible to delete a login ID if there are any unposted sales documents or reverse auctions containing the login ID.
All information that was used for the user to have access to the Web portal has now been deleted. This includes roles and notification process codes.
When you have removed a Web portal user's access to Commerce Portal, the user's status has now been changed to a normal contact. In other words, you have not deleted the user from Navision .