Thanks to RandomUs 1r for this observation:
changing it to display:inline-block; solves that issue. – RandomUs1r May 14 '13 at 21:59
I tried it myself for a top navigation menu bar, as follows:
First style the "li" element as follows:
display: inline-block;
width: 7em;
text-align: center;
Then style the "a"> element as follows:
width: 100%;
Now the navigation links are all equal width with text centered in each link.