[VE][73] for unfinished element, should point to definition

Error [73]: "end tag for X which is not finished"

To be more helpful, the error message should:
- at least point to the unfinished element's definition in some
   specification or in some validator-specific grammar page, and
- ideally, list at least one of the required sub-elements that was
   not present (so the user at least make one increment of progress
   by adding that element and trying again).



-- 
(Plain text sometimes corrupted to HTML "courtesy" of Microsoft Exchange.) [F]