A simple CSS-only dropdown menu.

dropdown-menu

.dropdown-menu {
  list-style: none;
  font-weight: bold;
  width: 100%;
  position: relative;
  z-index: 5;
  font-family: Sans-serif;
}
.dropdown-menu li {
  float: left;
  position: relative;
  margin-right: 2px;
}
.dropdown-menu li a:HOVER {
  background: #333;
  color: #fff;
  text-decoration: underline;
}
.dropdown-menu a {
  display: block;
  font-size: 15px;
  font-weight: bolder;
  font-family: sans-serif;
  background: #333;
  color: #fff;
  padding: 5px;
}
.dropdown-menu a:hover {
  color: #fff;
  background: #fafafa;
}
.dropdown-menu ul {
  background: #fff;
  list-style: none;
  position: absolute;
  left: -9999px;
}
.dropdown-menu ul li {
  float: none;
  margin: 0;
}
.dropdown-menu ul a {
  white-space: nowrap;
}
.dropdown-menu li:hover ul {
  left: 0;
  margin: 0;
}
.dropdown-menu li:hover ul a {
  text-decoration: none;
}
.dropdown-menu li:hover ul li a:hover {
  background: #fafafa;
  color: #333;
}