Next with edit line 206 #menu {z-index:203; width:685px; height:100px; position:relative; float:left; clear:none; padding:0; margin:0; background:none; font-weight:bold; font-size:123%; }

How can we fix this Problem? In which CSS-File can we find div#menu?

Your div#menu don't have ul.menu inside but only simple 'ul'.