How To Create a Dropdown Menu using css

HTML
<nav> <ul><li><a href="#">Home</a></li><li><a href="#">Tutorials</a> <ul><li><a href="#">Photoshop</a></li><li><a href="#">Illustrator</a></li><li><a href="#">Web Design</a> <ul><li><a href="#">HTML</a></li><li><a href="#">CSS</a></li></ul></li></ul></li><li><a href="#">Articles</a> <ul><li><a href="#">Web Design</a></li><li><a href="#">User Experience</a></li></ul></li><li><a href="#">Inspiration</a></li></ul></nav>
The secondary sub-menu is nested under the “Web Design” option of the first sub-menu. These links are placed into another unordered list and inserted into the “Web Design”

CSS Styling
nav ul ul {
display: none;
}
nav ul li:hover > ul {
display: block;
}

Let’s begin the CSS by getting the basic dropdown functionality working. With CSS specificity and advanced selectors we can target individual elements buried deep in the HTML structure without the need for extra IDs or classes. First hide the sub menus by targeting any UL’s within a UL with the display:block; declaration. In order to make these menus reappear they need to be converted back to block elements on hover of the LI. The > child selector makes sure only the child UL of the LI being hovered is targeted, rather than all sub menus appearing at once.

nav ul {
background: #efefef;
background: linear-gradient(top, #efefef 0%, #bbbbbb 100%);
background: -moz-linear-gradient(top, #efefef 0%, #bbbbbb 100%);
background: -webkit-linear-gradient(top, #efefef 0%,#bbbbbb 100%);
box-shadow: 0px 0px 9px rgba(0,0,0,0.15);
padding: 0 20px;
border-radius: 10px;
list-style: none;
position: relative;
display: inline-table;
}
nav ul:after {
content: ""; clear: both; display: block;
}

We can then start to style up the main navigation menu with the help of CSS3 properties such as gradients, box shadows and border radius. Adding position:relative; will allow us to absolutely position the sub menus according to this main nav bar, then display:inline-table will condense the width of the menu to fit. The clearfix style rule will clear the floats used on the subsequent list items without the use of overflow:hidden, which would hide the sub menus and prevent them from appearing.

nav ul li {
float: left;
}
nav ul li:hover {
background: #4b545f;
background: linear-gradient(top, #4f5964 0%, #5f6975 40%);
background: -moz-linear-gradient(top, #4f5964 0%, #5f6975 40%);
background: -webkit-linear-gradient(top, #4f5964 0%,#5f6975 40%);
}
nav ul li:hover a {
color: #fff;
}
nav ul li a {
display: block; padding: 25px 40px;
color: #757575; text-decoration: none;
}

The individual menu items are then styled up with CSS rules added to the <-li-> and the nested anchor. In the browser this will make the link change to a blue gradient background and white text.

nav ul ul {
background: #5f6975; border-radius: 0px; padding: 0;
position: absolute; top: 100%;
}
nav ul ul li {
float: none;
border-top: 1px solid #6b727c;
border-bottom: 1px solid #575f6a;
position: relative;
}
nav ul ul li a {
padding: 15px 40px;
color: #fff;
}

nav ul ul li a:hover {
background: #4b545f;
}

The main navigation bar is now all styled up, but the sub menus still need some work. They are currently inheriting styles from their parent elements, so a change of background and the removal of the border-radius and padding fixes their appearance. To make sure they fly out underneath the main menu they are positioned absolutely 100% from the top of the UL (ie, the bottom).
The LI’s of each UL in the sub menu don’t need floating side by side, instead they’re listed vertically with thin borders separating each one. A quick hover effect then darkens the background to act as a visual cue.

nav ul ul ul {
position: absolute; left: 100%; top:0;
}
The final step is to position the sub-sub-menus accordingly. These menus will be inheriting all the sub-menu styling already, so all they need is to be positioned absolutely to the right (left:100%) of the relative position of the parent .