Css - Can Someone Help Me Figure Out Where I Went Wrong With My Dropdown Menu Nav?

I wanted to learn how to create a dropdown nav bar in the simplest and cleanest way possible. I followed this wiki how CSS-only dropdown menu guide, but it seems my code is not com

Solution 1:

The li at level 1 should has property position:relative, so that the child ul will be able to set the position according to its parent. I make some changes, see the fiddle: click here