The documentation here seems rather un-detailed. http://orgmode.org/manual/Tables-in-HTML-export.html#Tables-in-HTML-export
What I wanted to do was to have vertical rules between all columns, but not horizontal rules. Neither this section of the documentation, nor the docstring for org-html-table-default-attributes, provide any details on how to do this.
It's a rather busy day and I'm not in the mood to scour through the elisp sources, so, could someone please enlighten (and fix the docs)?
hjh