djeyewater's thread contains a good discussion describing a particular style of spacing horizontal menus. In the second thread, Paul adds other CSS choices including the popular "text justify" method. That's an especially informative thread because it is the contest in which the technique is thoroughly discussed.
Your post did not indicate much about what you want to achieve, so I posted some links where you can find a variety of horizontal menu spacing examples and maybe identify one that you want to replicate. Paul's code is already available in his posts, which makes it easy to harvest.
Good reading and good luck.