Ho modificato il css come segue:
codice:
#chromemenu{
width: 760px;
background-color: #f0f0f0;
border-left: 1px solid #ccc;
border-right: 1px solid #ccc;
border-bottom: 1px solid #ccc;
}

#chromemenu:after{ /*Add margin between menu and rest of content in Firefox*/
content: "."; 
display: block; 
height: 0; 
clear: both; 
visibility: hidden;
}

#chromemenu ul{
width: 100%;
margin-left: 0;
padding-left: 0;
margin: 0;
font: bold 12px Verdana;
text-align: center
}


#chromemenu ul li{
display: inline;
height: 0px;
}


#chromemenu ul li a{
color: #004e90;
font-weight: bold;
padding: 6px 12px 6px 7px;
text-decoration: none;
}

#chromemenu ul li a:hover{
color: #df0007;
}

/* ######### Style for Drop Down Menu ######### */

.dropmenudiv{
position:absolute;
top: 0;
border: 1px solid #e7e7e7; /*Theme Change here*/
border-bottom-width: 0;
font:normal 12px Verdana;
line-height:18px;
z-index:100;
background-color: #f0f0f0;
width: 200px;
visibility: hidden;
filter: progid:DXImageTransform.Microsoft.Shadow(color=#ccc,direction=135,strength=2); /*Add Shadow in IE. Remove if desired*/
}

.dropmenudiv a{
width: 100%;
display: block;
text-indent: 3px;
border-bottom: 1px solid #e2e2e2; /*Theme Change here*/
padding: 2px 0;
text-decoration: none;
font-weight: bold;
color: #004e90;
}

.dropmenudiv a:hover{ /*Theme Change here*/
background-color: #e7e7e7;
color: #df0007;
}
Ma non ho avuto il risultato sperato. :master: