[Sisom]

Hi, I think what you need to do is to add the declaration:
display: inline;

to the style for
.menu-bestsellers ul li

In V4.2 it's in altskin.css, line 571, along with some other selectors, so you would just need to add
.menu-bestsellers ul li {
display: inline;
padding: 0 20px 0 0;
}

after
.menu-categories-list ul li, .menu-minicart ul li, .menu-bestsellers ul li, .menu-special ul li {
background:url("images/2column/bullet_white.gif") no-repeat scroll 0 7px transparent;
border-bottom:1px solid white;
font-size:1em;


(I recommend you use Firebug, a Firefox add on, to edit your site. I only found out about it through this forum, two weeks ago, and it has saved me literally days of my time.)