I’m trying to get a CSS-only drop-down menu working. It largely does work except for the fact that other content appears to be showing through and I can’t work out why.
Could someone tell me what I’m doing wrong? CSS not my strong suit.

The drop-down is appearing in the correct position, but you can see the other “test” links showing through. In the image, the bottom two “test” links should be hidden by the presence of the dropdown.
TIA
(2nd attempt)
Ok, if I understand correctly all you need to do is move the z-index to the ULs: