org-html-table-row-tags

org-html-table-row-tags is a variable defined in `ox-html.el'.
Its value is

("" . "")

Documentation:
The opening and ending tags for table rows.
This is customizable so that alignment options can be specified.
Instead of strings, these can be Lisp forms that will be
evaluated for each row in order to construct the table row tags.

During evaluation, these variables will be dynamically bound so that
you can reuse them:

`row-number': row number (0 is the first row)
`rowgroup-number': group number of current row
`start-rowgroup-p': non-nil means the row starts a group
`end-rowgroup-p': non-nil means the row ends a group
`top-row-p': non-nil means this is the top row
`bottom-row-p': non-nil means this is the bottom row

For example:

(setq org-html-table-row-tags
(cons '(cond (top-row-p "")
(bottom-row-p "")
(t (if (= (mod row-number 2) 1)
""
"")))
""))

will use the "tr-top" and "tr-bottom" classes for the top row
and the bottom row, and otherwise alternate between "tr-odd" and
"tr-even" for odd and even rows.

You can customize this variable.