24. Menú horizontal  3 niveles!!!

http://campamentoweb.blogspot.com.es/2014/01/menu-horizontal-desplegable-solo-con-css.html#.V4ZPKdSLSig

<div id='cssmenu'>
<ul>
   <li class='active'><a href='index.html'><span>Home</span></a></li>
   <li class='has-sub'><a href='#'><span>Products</span></a>
      <ul>
         <li class='has-sub'><a href='#'><span>Product 1</span></a>
            <ul>
               <li><a href='#'><span>Sub Item</span></a></li>
               <li class='last'><a href='#'><span>Sub Item</span></a></li>
            </ul>
         </li>
         <li class='has-sub'><a href='#'><span>Product 2</span></a>
            <ul>
               <li><a href='#'><span>Sub Item</span></a></li>
               <li class='last'><a href='#'><span>Sub Item</span></a></li>
            </ul>
         </li>
      </ul>
   </li>
   <li><a href='#'><span>About</span></a></li>
   <li class='last'><a href='#'><span>Contact</span></a></li>
</ul>
</div>

Cambiar CSS

 #cssmenu > ul {
  position: relative;
  z-index: 597;
  float: left;
 position: absolute;
top: 235px;
left: 100px;
  background-image:  linear-gradient(135deg, rgba(154,142,193,1) 0%, rgba(154,142,193,0.96) 10%, rgba(174,164,205,0.92) 20%, rgba(242,242,242,0.87) 35%, rgba(242,242,242,0.75) 65%, rgba(174,164,205,0.7) 80%, rgba(154,142,193,0.66) 90%, rgba(154,142,193,0.62) 100%);

CSS

/* Base Styles */
#cssmenu > ul,
#cssmenu > ul li,
#cssmenu > ul ul {
  list-style: none;
  margin: 0;
  padding: 0;
}
#cssmenu > ul {
  position: relative;
  z-index: 597;
  float: left;
}
#cssmenu > ul li {
  float: left;
  min-height: 1px;
  line-height: 1.3em;
  vertical-align: middle;
  padding: 10px;
}
#cssmenu > ul li.hover,
#cssmenu > ul li:hover {
  z-index: 599;
  cursor: default;
}
#cssmenu > ul ul {
  visibility: hidden;
  position: absolute;
  top: 100%;
  left: 0;
  z-index: 598;
}
#cssmenu > ul ul li {
  float: none;
}
#cssmenu > ul li:hover > ul {
  visibility: visible;
}
/* Align last drop down RTL */
/* Theme Styles */
#cssmenu > ul a:link {
  text-decoration: none;
}
#cssmenu > ul a:active {
  color: #ffa500;
}
#cssmenu li {
  padding: 0;
  color: #000;
}
#cssmenu {
  font-family: 'Lato', sans-serif;
  width: auto;
  -webkit-border-radius: 3px;
  -moz-border-radius: 3px;
  -ms-border-radius: 3px;
  -o-border-radius: 3px;
  border-radius: 3px;
  background: #1b9bff;
  font-size: 13px;
  -moz-box-shadow: inset 0 2px 2px rgba(255, 255, 255, 0.3);
  -webkit-box-shadow: inset 0 2px 2px rgba(255, 255, 255, 0.3);
  box-shadow: inset 0 2px 2px rgba(255, 255, 255, 0.3);
}
#cssmenu > ul {
  padding: 0 5px;
  -moz-box-shadow: inset 0 -2px 2px rgba(0, 0, 0, 0.3);
  -webkit-box-shadow: inset 0 -2px 2px rgba(0, 0, 0, 0.3);
  box-shadow: inset 0 -2px 2px rgba(0, 0, 0, 0.3);
  -webkit-border-radius: 3px;
  -moz-border-radius: 3px;
  -ms-border-radius: 3px;
  -o-border-radius: 3px;
  border-radius: 3px;
  display: block;
  float: none;
  zoom: 1;
}
#cssmenu > ul:before {
  content: '';
  display: block;
}
#cssmenu > ul:after {
  content: '';
  display: table;
  clear: both;
}
#cssmenu > ul > li {
  padding: 8px 5px;
}
#cssmenu > ul > li > a,
#cssmenu > ul > li > a:link,
#cssmenu > ul > li > a:visited {
  text-shadow: 0 -1px 1px #004881;
  color: #fff;
  padding: 7px 20px;
  display: block;
  -webkit-border-radius: 3px;
  -moz-border-radius: 3px;
  -ms-border-radius: 3px;
  -o-border-radius: 3px;
  border-radius: 3px;
}
#cssmenu > ul > li > a:hover,
#cssmenu > ul > li:hover > a {
  background-color: #0082e7;
}
#cssmenu li li a {
  color: #8b8b8b;
  font-size: 13px;
}
#cssmenu li li a:hover {
  color: #5c5c5c;
  border-color: #5c5c5c;
}
#cssmenu ul ul {
  margin: 0 10px;
  padding: 0 10px;
  float: none;
  background: #efefef;
  border: 2px solid #1b9bff;
  border-top: none;
  right: 0;
  left: 0;
  -webkit-border-radius: 0 0 3px 3px;
  -moz-border-radius: 0 0 3px 3px;
  -ms-border-radius: 0 0 3px 3px;
  -o-border-radius: 0 0 3px 3px;
  border-radius: 0 0 3px 3px;
  -moz-box-shadow: 0 2px 3px rgba(0, 0, 0, 0.2);
  -webkit-box-shadow: 0 2px 3px rgba(0, 0, 0, 0.2);
  box-shadow: 0 2px 3px rgba(0, 0, 0, 0.2);
}
#cssmenu ul > li > ul > li {
  margin: 0 10px 0 0;
  position: relative;
  padding: 0;
  float: left;
}
#cssmenu ul > li > ul > li > a {
  padding: 10px 20px 10px 10px;
  display: block;
}
#cssmenu ul > li > ul > li.has-sub > a:before {
  content: '';
  position: absolute;
  top: 18px;
  right: 6px;
  border: 5px solid transparent;
  border-top: 5px solid #8b8b8b;
}
#cssmenu ul > li > ul > li.has-sub > a:hover:before {
  border-top: 5px solid #5c5c5c;
}
#cssmenu ul ul ul {
  width: 200px;
  top: 100%;
  border: 2px solid #1b9bff;
}
#cssmenu ul ul ul li {
  float: none;
}