HTML
<div id="Navigation">
<ul id="nav">
<li id="active"><a href="#" id="cu">Item number 1</a></li>
<li><a href="#">Item number 2</a></li>
<li><a href="#">Item number 3</a></li>
<li><a href="#">Item number 4</a></li>
<li><a href="#">Item number 5</a></li>
</ul>
</div>

CSS
#Navigation
{
margin: 0;
padding: 0;
height: 22px;
font: 11px Verdana, sans-serif;
width: 100%;
border-bottom: 1px solid #bbb;
list-style-type: none;
background: #eee;
}

#nav li
{
float: left;
margin: 0;
padding: 0;
width: auto;
display: block;
}

#nav li a, #nav li a:link
{
background: #eee;
color: #555;
text-decoration: none;
padding: 3px 5px 3px 5px;
display: block;
}

#nav li a:hover
{
color: #039;
border-bottom: 3px solid #bbb;
cursor: pointer;
background: #fff;
}

#nav li a#cu, #nav li a#cu:link
{
color: #000;
font-weight: bold;
border-bottom: 3px solid #999;
}

#nav li a#cu:hover
{
border-bottom: 3px solid #f90;
background: #fff;
}