Making Menu Display Horizontally

Sure, just add some css rules. For example…

#id-of-top-ul li {display:inline-block; vertical-align:top;}
#id-of-top-ul li li {display:list-item;}

or

#id-of-top-ul li {float:left;}
#id-of-top-ul li li {float:none;}

These are just a couple of possibilities, and there are undoubtedly other (and possibly better) alternatives. They are also merely starting points : you will probably want to tweak some other settings as well (to give some horizontal separation, for example), and the relative success of any particular method may depend on your specific menu structure (particularly the number of sub-items if you use float).