#navigation  { float: left; width: 120px; background: #e2e2e2;
               margin-top: 10px; border: 1px solid #c8c8c8; z-index:3;
               position: absolute; } 
               <!-- Anweisung (absolute) für Safari! -->

#gaeste  { width: 400px; background: #e8e8e8; float: center; margin-left: 110px; 
           border: 1px solid #cbcbcb;}