Sorry for the late reply. I wouldn't use a linked field for this, since you won't be able to edit that data from the Edit Customer screen. I would add a new Website field to the Customer table, then put actions in on the save and load events. On the save, use an Update Field in Table action to update the Website field in the Contacts table. For the load events (OnScreenLoad and OnClosePopup), include actions that will update the field from the Contacts Website field.
The idea is to have the two fields match whenever a value is added or changed in either field.
Hope this helps,