This blog has a satisfyingly robust solution. It needs some slight changes to accommodate a ul/li
navigation, though:
#Navigation {
width: 100%;
padding: 0;
text-align: justify;
font-size: 0;
font-size: 12px\9; /* IE 6-9 */
}
#Navigation>li {
font-size: 12px;
text-align: center;
display: inline-block;
zoom: 1;
*display: inline; /* IE only */
}
#Navigation:after {
content:"";
width: 100%;
display: inline-block;
zoom: 1;
*display: inline;
}
http://jsfiddle.net/mblase75/9vNBs/