Exemplo de menu horizontal totalmente em CSS e XHTML.

Abaixo o código do CSS e do XHTML para formar o menu:

Estrutura do Menu:


<div class="underlinemenu">
<ul>
<li><a href="/">Home</a></li>
<li><a href="/">CSS Codes</a></li>
<li><a href="/">Forums</a></li>
<li><a href="/">Webmaster Tools</a></li>
<li><a href="/">JavaScript</a></li>
<li><a href="/">Gallery</a></li>
</ul>
</div>


Estilo do Menu:


<style type="text/css">

/*Credits: Dynamic Drive CSS Library */
/*URL: http://www.dynamicdrive.com/style/ */

.underlinemenu{
font-weight: bold;
width: 100%;
}

.underlinemenu ul{
padding: 6px 0 7px 0; /*6px should equal top padding of "ul li a" below, 7px should equal bottom padding + bottom border of "ul li a" below*/
margin: 0;
text-align: right; //set value to "left", "center", or "right"*/
}

.underlinemenu ul li{
display: inline;
}

.underlinemenu ul li a{
color: #494949;
padding: 6px 3px 4px 3px; /*top padding is 6px, bottom padding is 4px*/
margin-right: 20px; /*spacing between each menu link*/
text-decoration: none;
border-bottom: 3px solid gray; /*bottom border is 3px*/
}

.underlinemenu ul li a:hover, .underlinemenu ul li a.selected{
border-bottom-color: black;
}

</style>