Resolving HTML validation "Warning: trimming empty tag"

Question: what about placing &a开发者_JAVA百科mp;nbsp; as the contents of the empty tag?

It validates, but is that considered a hack?

Regarding your question and with the detail from your comment, it is not a hack, but it is most likely not best practice either.

If you are looking to have a blank item for default, I would recommend --Select One-- instead, and if you are looking for a divider -------- would probably be your best option.