Grazie!
Ecco come ho risolto:
body{
background-color:
#c2c3c1;
}
#menu_sito{
padding:0;
margin:0;
z-index: 1000;
} ul{
padding:0;
margin:0;
font: italic bold 18px Georgia, "Times New Roman", Times, serif;
} li{
position: relative;
float: left;
list-style: none;
margin: 0;
padding:0;
z-index: 1000;
} li a{
height: 40px;
display: block;
text-decoration:none;
text-align: left;
line-height: 40px;
color:
#333;
background: none;
z-index: 1000;
padding-left:12px;
padding-right: 12px;
} li a:hover{
background: none;
} ul li:hover ul{
visibility:visible;
z-index: 1000;
} ul li:hover ul ul{
visibility:hidden;
z-index: 1000;
} ul ul{
position: absolute;
top: 40px;
visibility: hidden;
font: 14px Arial, Helvetica, sans-serif;
z-index: 1000;
background-color: cadetblue;
text-align:left;
} ul ul li a{
height: 30px;
display: block;
text-decoration:none;
text-align: left;
line-height: 30px;
color:;
background: none;
z-index: 1000;
width: 176px;
} ul ul li a:hover{
background:
#171717;
color:
#f87a2b;
} ul ul li:hover ul{
visibility:visible;
} ul ul ul{
visibility: hidden;
position:absolute;
left:200px;
top:0;
background-color: black;
width: 200px;
} ul ul ul li a{
margin:0;
height: 30px;
display: block;
text-decoration:none;
text-align: left;
color:;
background: none;
z-index: 1000;
} ul ul ul li a:hover{
background: yellow;
}