/* general styles */
.menu, .menu ul {
  list-style: none;
  padding: 0;
  margin: 0;
}
.menu {
  height: 58px;
}
.menu li {
  background: -moz-linear-gradient(#292929, #252525);
  background: -ms-linear-gradient(#292929, #252525);
  background: -webkit-gradient(linear, left top, left bottom, color-stop(0%, #292929), color-stop(100%, #252525));
  background: -webkit-linear-gradient(#292929, #252525);
  background: -o-linear-gradient(#292929, #252525);
  filter: progid:DXImageTransform.Microsoft.gradient(startColorstr='#292929', endColorstr='#252525');
  -ms-filter: "progid:DXImageTransform.Microsoft.gradient(startColorstr='#292929', endColorstr='#252525')";
  background: linear-gradient(#292929, #252525);

  border-bottom: 2px solid #181818;
  border-top: 2px solid #303030;
  min-width: 160px;
}
.menu > li {
  display: block;
  float: left;
  position: relative;
}
.menu > li:first-child {
  border-radius: 5px 0 0;
}
.menu a {
  border-left: 3px solid rgba(0, 0, 0, 0);
  color: #808080;
  display: block;
  font-family: 'Lucida Console';
  font-size: 18px;
  line-height: 54px;
  padding: 0 25px;
  text-decoration: none;
  text-transform: uppercase;
}

/* onhover styles */
.menu li:hover {
  background-color: #1c1c1c;
  background: -moz-linear-gradient(#1c1c1c, #1b1b1b);
  background: -ms-linear-gradient(#1c1c1c, #1b1b1b);
  background: -webkit-gradient(linear, left top, left bottom, color-stop(0%, #1c1c1c), color-stop(100%, #1b1b1b));
  background: -webkit-linear-gradient(#1c1c1c, #1b1b1b);
  background: -o-linear-gradient(#1c1c1c, #1b1b1b);
  filter: progid:DXImageTransform.Microsoft.gradient(startColorstr='#1c1c1c', endColorstr='#1b1b1b');
  -ms-filter: "progid:DXImageTransform.Microsoft.gradient(startColorstr='#1c1c1c', endColorstr='#1b1b1b')";
  background: linear-gradient(#1c1c1c, #1b1b1b);

  border-bottom: 2px solid #222222;
  border-top: 2px solid #1B1B1B;
}
.menu li:hover > a {
  border-radius: 5px 0 0 0;
  border-left: 3px solid #C4302B;
  color: #C4302B;
}

/* submenu styles */
.submenu {
  left: 0;
  max-height: 0;
  position: absolute;
  top: 100%;
  z-index: 0;

  -webkit-perspective: 400px;
  -moz-perspective: 400px;
  -ms-perspective: 400px;
  -o-perspective: 400px;
  perspective: 400px;
}
.submenu li {
  opacity: 0;

  -webkit-transform: rotateY(90deg);
  -moz-transform: rotateY(90deg);
  -ms-transform: rotateY(90deg);
  -o-transform: rotateY(90deg);
  transform: rotateY(90deg);

  -webkit-transition: opacity .4s, -webkit-transform .5s;
  -moz-transition: opacity .4s, -moz-transform .5s;
  -ms-transition: opacity .4s, -ms-transform .5s;
  -o-transition: opacity .4s, -o-transform .5s;
  transition: opacity .4s, transform .5s;
}
.menu .submenu li:hover a {
  border-left: 3px solid #454545;
  border-radius: 0;
  color: #ffffff;
}
.menu > li:hover .submenu, .menu > li:focus .submenu {
  max-height: 2000px;
  z-index: 10;
}
.menu > li:hover .submenu li, .menu > li:focus .submenu li {
  opacity: 1;

  -webkit-transform: none;
  -moz-transform: none;
  -ms-transform: none;
  -o-transform: none;
  transform: none;
}

/* CSS3 delays for transition effects */
.menu li:hover .submenu li:nth-child(1) {
  -webkit-transition-delay: 0s;
  -moz-transition-delay: 0s;
  -ms-transition-delay: 0s;
  -o-transition-delay: 0s;
  transition-delay: 0s;
}
.menu li:hover .submenu li:nth-child(2) {
  -webkit-transition-delay: 50ms;
  -moz-transition-delay: 50ms;
  -ms-transition-delay: 50ms;
  -o-transition-delay: 50ms;
  transition-delay: 50ms;
}
.menu li:hover .submenu li:nth-child(3) {
  -webkit-transition-delay: 100ms;
  -moz-transition-delay: 100ms;
  -ms-transition-delay: 100ms;
  -o-transition-delay: 100ms;
  transition-delay: 100ms;
}
.menu li:hover .submenu li:nth-child(4) {
  -webkit-transition-delay: 150ms;
  -moz-transition-delay: 150ms;
  -ms-transition-delay: 150ms;
  -o-transition-delay: 150ms;
  transition-delay: 150ms;
}
.menu li:hover .submenu li:nth-child(5) {
  -webkit-transition-delay: 200ms;
  -moz-transition-delay: 200ms;
  -ms-transition-delay: 200ms;
  -o-transition-delay: 200ms;
  transition-delay: 200ms;
}
.menu li:hover .submenu li:nth-child(6) {
  -webkit-transition-delay: 250ms;
  -moz-transition-delay: 250ms;
  -ms-transition-delay: 250ms;
  -o-transition-delay: 250ms;
  transition-delay: 250ms;
}
.menu li:hover .submenu li:nth-child(7) {
  -webkit-transition-delay: 300ms;
  -moz-transition-delay: 300ms;
  -ms-transition-delay: 300ms;
  -o-transition-delay: 300ms;
  transition-delay: 300ms;
}
.menu li:hover .submenu li:nth-child(8) {
  -webkit-transition-delay: 350ms;
  -moz-transition-delay: 350ms;
  -ms-transition-delay: 350ms;
  -o-transition-delay: 350ms;
  transition-delay: 350ms;
}

.submenu li:nth-child(1) {
  -webkit-transition-delay: 350ms;
  -moz-transition-delay: 350ms;
  -ms-transition-delay: 350ms;
  -o-transition-delay: 350ms;
  transition-delay: 350ms;
}
.submenu li:nth-child(2) {
  -webkit-transition-delay: 300ms;
  -moz-transition-delay: 300ms;
  -ms-transition-delay: 300ms;
  -o-transition-delay: 300ms;
  transition-delay: 300ms;
}
.submenu li:nth-child(3) {
  -webkit-transition-delay: 250ms;
  -moz-transition-delay: 250ms;
  -ms-transition-delay: 250ms;
  -o-transition-delay: 250ms;
  transition-delay: 250ms;
}
.submenu li:nth-child(4) {
  -webkit-transition-delay: 200ms;
  -moz-transition-delay: 200ms;
  -ms-transition-delay: 200ms;
  -o-transition-delay: 200ms;
  transition-delay: 200ms;
}
.submenu li:nth-child(5) {
  -webkit-transition-delay: 150ms;
  -moz-transition-delay: 150ms;
  -ms-transition-delay: 150ms;
  -o-transition-delay: 150ms;
  transition-delay: 150ms;
}
.submenu li:nth-child(6) {
  -webkit-transition-delay: 100ms;
  -moz-transition-delay: 100ms;
  -ms-transition-delay: 100ms;
  -o-transition-delay: 100ms;
  transition-delay: 100ms;
}
.submenu li:nth-child(7) {
  -webkit-transition-delay: 50ms;
  -moz-transition-delay: 50ms;
  -ms-transition-delay: 50ms;
  -o-transition-delay: 50ms;
  transition-delay: 50ms;
}
.submenu li:nth-child(8) {
  -webkit-transition-delay: 0s;
  -moz-transition-delay: 0s;
  -ms-transition-delay: 0s;
  -o-transition-delay: 0s;
  transition-delay: 0s;
}

<ul class="menu">
  <li><a href="#">Главная</a></li>
  <li><a href="#s1">Галерея</a>
  <ul class="submenu">
  <li><a href="#">Submenu a</a></li>
  <li><a href="#">Submenu b</a></li>
  <li><a href="#">Submenu c</a></li>
  <li><a href="#">Submenu d</a></li>
  <li><a href="#">Submenu e</a></li>
  <li><a href="#">Submenu f</a></li>
  <li><a href="#">Submenu g</a></li>
  <li><a href="#">Submenu h</a></li>
  </ul>
  </li>
  <li class="active"><a href="#s2">Файлы</a>
  <ul class="submenu">
  <li><a href="#">Submenu a</a></li>
  <li><a href="#">Submenu b</a></li>
  <li><a href="#">Submenu c</a></li>
  <li><a href="#">Submenu d</a></li>
  <li><a href="#">Submenu e</a></li>
  <li><a href="#">Submenu f</a></li>
  <li><a href="#">Submenu g</a></li>
  <li><a href="#">Submenu h</a></li>
  </ul>
  </li>
  <li><a href="#">Блог</a>
  <ul class="submenu">
  <li><a href="#">Submenu a</a></li>
  <li><a href="#">Submenu b</a></li>
  <li><a href="#">Submenu c</a></li>
  <li><a href="#">Submenu d</a></li>
  <li><a href="#">Submenu e</a></li>
  <li><a href="#">Submenu f</a></li>
  <li><a href="#">Submenu g</a></li>
  <li><a href="#">Submenu h</a></li>
  </ul>
  </li>
</ul>