Your styles, clear: left and clear: right on the first and last li serve no purpose, they can go.

Take the display: block out of the navcontainer definition as div's are by default bloack elements and put it in your a: definition as this wil make them active for the full width of the li containing them.

Give the navcontainer a position: relative. No need for aany actual positional info. Your just defining an anchor so to to speak for the li's it contains.

Float your li's left with suitable left margin on the first one to position the start of the links.

Give your navcontainer a suitable height.

Then lets see where we are.