#menuv {
position:relative;
}
#menuv {
position:absolute;
left:50%;top:0;
margin-left:-225px; /* negative margin equal to half the width */
width:750px;
list-style:none;
}
#menuv li {
float:left;
}
#menuv a {
display:block;
text-align:center;
width:150px; /* fixed width */
text-decoration:none; 
}