How to change padding on menu items

The menu we have at present (see http://dowsingworldsummit.com/faqs/) is too long to display in FF and cannot be scrolled to see the last item. I would like to be able to reduce the padding of the elements and / or reduce the font size to make all items readable.

I’ve tried altering the top and bottom padding of sub-menu a but without any luck.

Can you please tell me what I should be doing to achieve what I am after?

Thanks

EDIT:

Found it… I needed to alter #top .main_menu .menu li ul a to change the padding.