Sorry but here's another question...
Some days ago I wanted to write something like this :
But I couldn't write correct code so I changed my mind & I styled my training page's navigation this way :
Yesterday & after dear ralph.m solution, thought I can style navigation as I want using the display:table & table-cell.
It works generally but there are some problems there with borders & center-aligned nav, etc :
Now I'm looking for your helps.