Well, you can of course not change HTML structure by changin CSS…
You have to modify the theme and put a link around the whole elements you want to link.
Beware of block level elements within inline elements! In HTML5 it is allowed to wrap links being inline ones around block level elements like div or headlines, on older HTML/XHTML standards it is invalid. Even if using HTML5 some older browsers will not recognize it and therefore ignore it completely respectively cause weird behaviour.
This is rather web technique basics actually.
