scusate ma non mi entrava tutto sul primo post:

//questo è il CSS che ho applicato all' xhtml del post precedente

body{
margin:0;
padding:0;
text-align: center;
}

#footer{
background:#787878;
width: 802px;
height: 900px;
}

#complex{
width: 802px;
margin-left: auto;
margin-right: auto;
text-align: left;
}

#reteup{
background: #787878;
}
#retedown{
background: #787878;
}

#contents{
float: left;
width: 200px;
background: #000000;
}
#menu ul{
margin:0px 0 0 0;
padding:0 0px 0 10px;
background:#444444;
color:#FFF;
font-size:100%;
font-weight:normal;
height: 20px;
list-style:none;

}
#menu li{
float:right;

}
#menu ul a{
padding:0 20px 0 6px;
float:left;
line-height:1.5em;
height: 20px;
background:url(linea.gif) #444444 right center no-repeat;
font-family: Verdana, Arial, Helvetica, sans-serif;
font-size: 12px;

}

a {
color: #999999;
}
#uno a:hover {
color: #ffcc00;
text-decoration: none;
}
#due a:hover {
color: #009900;
text-decoration: none;
}
#tre a:hover {
color: #ffffff;
text-decoration: none;
}