Making wordpress menu horizontal [closed]

If I understood correctly you are trying to position output of wp_nav_menu() in horizontal line. Your should try styling <li> elements, instead of all <div>. Also width: 100%; should be removed.

Something like this seems to work:

.mythirdclass li {
   float: left;
   padding: 0;
   margin: 1em;
   list-style-type: none;
   display: inline;

}