Nn va... mi rimane spostato sulla sinistra, dove sbaglio?:

#mainmenu ul
{
list-style-type: none;
margin-left: 0px;
padding-left: 0px;
display: inline;
}

#mainmenu a
{

color: #FFFFFF;
background-color: #000000;
width: 100%;
padding-right: 5px;
text-decoration: none;
text-align: left;
font-family: Arial, Helvetica, sans-serif;
font-size: 14px;
font-weight: bold;
}

#mainmenu a:hover
{
background-color: #FFFFFF;
color: #000000;
text-align: left;
}

#mainmenu li {
list-style-type: none;
display: inline;}