css menu hover“hangs”在铬&苹果浏览器

问候 -
使用三级css菜单。

在FireFox和Opera中适用于Mac，但在Chrome和Safari中，第三级stick或hangs将光标移开后的水印。

Greetings - Struggeling with a three-level css menu.
Works fine in FireFox and Opera for mac, but in Chrome and Safari the third level "sticks" or "hangs" as a watermark after you move the cursor away.

我试过了几个不同的东西，没有运气。

I have tried a few different things without luck.

在此演示：

http://www.it-stud.hiof.no/~benteh/tmp/

我已经切掉了一切，所以这只是菜单css& html。

（PS。考古，人类和环境只有三个层次）

I have cut away everything else, so this is just the menu css & html.
(PS. there are only three levels on archeology, hominins and environmental)