Recently, Web Designer Wall posted this really cool tutorial on creating a dropdown menu using only CSS3 (no javascript). Not being one to just sit back and let things sit as is, the approach inspired me make a variation. The result, however directly derivitive, is this horizonatal drop line menu based on a variation of WDW's tut.

The XHTML markup:

<div id="menu">

<ul id="nav">
<li><a href="#">Menu 1</a>
 <ul>
 <li><a href="#">Menu 1 Submenu item 1</a></li>
 <li><a href="#">Menu 1 Submenu item 2</a></li>
 <li><a href="#">Menu 1 Submenu item 3</a></li>
 </ul>
</li>

<li><a href="#">Menu 2</a>
 <ul>
 <li><a href="#">Menu 2 Submenu item 1</a></li>
 <li><a href="#">Menu 2 Submenu item 2</a></li>
 <li><a href="#">Menu 2 Submenu item 3</a></li>
 </ul>
</li>

<li><a href="#">Menu 3</a>
 <ul>
 <li><a href="#">Menu 3 Submenu item 1</a></li>
 <li><a href="#">Menu 3 Submenu item 2</a></li>
 <li><a href="#">Menu 3 Submenu item 3</a></li>
 </ul>
</li> 
</ul>

</div>

The CSS:

#menu {
  width: 960px;
  height: 40px;
  clear: both;
}

ul#nav {
  float: left;
  width: 960px;
  margin: 0;
  padding: 0;
  list-style: none;
  background: #dc0000 url(../img/menu-parent.png) repeat-x;
  -moz-border-radius-topright: 10px;
  -webkit-border-top-right-radius: 10px;
  -moz-border-radius-topleft: 10px;
  -webkit-border-top-left-radius: 10px;  
}

ul#nav li {
  display: inline;
}

ul#nav li a {
  float: left;
  font: bold 1.1em arial,verdana,tahoma,sans-serif;
  line-height: 40px;
  color: #fff;
  text-decoration: none;
  text-shadow: 1px 1px 1px #880000;
  margin: 0;
  padding: 0 30px;
  background: #dc0000 url(../img/menu-parent.png) repeat-x;
  -moz-border-radius-topright: 10px;
  -webkit-border-top-right-radius: 10px;
  -moz-border-radius-topleft: 10px;
  -webkit-border-top-left-radius: 10px;     
}

/* APPLIES THE ACTIVE STATE */
ul#nav .current a, ul#nav li:hover > a  {
  color: #fff;
  text-decoration: none;
  text-shadow: 1px 1px 1px #330000;
  background: #bb0000;
  -moz-border-radius-topright: 10px;
  -webkit-border-top-right-radius: 10px;
  -moz-border-radius-topleft: 10px;
  -webkit-border-top-left-radius: 10px; 
}

/* THE SUBMENU LIST HIDDEN BY DEFAULT */
ul#nav  ul {
  display: none;
}

/* WHEN THE FIRST LEVEL MENU ITEM IS HOVERED, THE CHILD MENU APPEARS */
ul#nav li:hover > ul {
  position: absolute;
  display: block;
  width: 920px;
  height: 45px;
  position: absolute;
  margin: 40px 0 0 0;
  background: #aa0000 url(../img/menu-child.png) repeat-x;  
  -moz-border-radius-bottomright: 10px;
  -webkit-border-bottom-right-radius: 10px;
  -moz-border-radius-bottomleft: 10px;
  -webkit-border-bottom-left-radius: 10px; 
}

ul#nav li:hover > ul li a {
  float: left;
  font: bold 1.1em arial,verdana,tahoma,sans-serif;
  line-height: 45px;
  color: #fff;
  text-decoration: none;
  text-shadow: 1px 1px 1px #110000;
  margin: 0;
  padding: 0 30px 0 0;
  background: #aa0000 url(../img/menu-child.png) repeat-x; 
}

ul#nav li:hover > ul li a:hover {
  color: #120000;
  text-decoration: none;
  text-shadow: none;
}