I ran into an issue with a field constraint not appearing in Web Access.  In the LF Client, the constraint "\d{4}-200" was being enforced appropriately and even displayed as "    -200".  In Web Access, the predetermined formatting wasn't shown, and the user can type freely in the field as if there are no constraints in place.

Edit: upon further investigation, the only issue is that WA doesn't display the mask or limit character input like the Client.  WA will allow anything to be typed and display a generic (does not meet constraint) message.