How to make such a submenu?

Question

css

Good day. Can't stretch submenu background to full screen height. With the root points, it seems that the issue was resolved, but the problem is with the sub-point.

What it looks like:


How it should:

Answer 1

For a block containing sub-items
display: inline-block;
position: absolute;
top:0;
bottom:0;
For a block containing items
position: absolute;
A block containing sub-items must follow the item.
JSfiddle
PS Using ul li for menus is somewhat wrong. Once there was a big controversy. And we came to the conclusion that it is more semantically not to use it. And do not produce extra blocks, tag A always has to be invested in LI. But many people remain unconvinced.