CSS Newbie

Last week, CSSnewbie reader Andrea Pluhar wrote in with an interesting problem: she wanted to use CSS dropdown menus like the ones we featured last week on a website that she was building, but the design called for the submenu to be arranged horizontally, not vertically. She sent me a mockup of what she was after (excerpted above) and wondered if there was a way to accomplish this effect using CSS. It turns out that there is a CSS-riffic way to do this, and in the spirit of maximizing benefit, I thought a tutorial would be in order.

The XHTML involved is identical to that used in our regular dropdown menus: a nested unordered list, where the nested lists become the submenus. It looks something like this:

<ul id="navbar">
	<li><a href="#">Item One</a><ul>
		<li><a href="#">Subitem One</a></li>
		<li><a href="#">Second Subitem</a></li>
		<li><a href="#">Numero Tres</a></li></ul>
	</li>
	<!-- ... and so on ... -->
</ul>

Next we’ll move to the CSS. I started out by moving the navigation bar to the top-right corner, like the design called for, removing the list styling, and floating the items left to make them line up in a row:

#navbar {
	position: absolute;
	top: 0;
	right: 0;
	margin: 0;
	padding: 0;}
#navbar li {
	list-style: none;
	float: left; }

Next, I styled the primary anchor tags to make them look more like the navigation Andrea was looking for. The code looks like this:

#navbar li a {
	display: block;
	padding: 3px 8px;
	text-transform: uppercase;
	text-decoration: none;
	color: #999;
	font-weight: bold; }
#navbar li a:hover {
	color: #000; }

I’ve added a bit of padding to the link, and used the text-transform property to make everything uppercase like the mockup called for. That way, the original XHTML can be lowercase or camel-case (capitalized first letters)… which would be a little easier to read in an unstyled document.

Next up, we hide the nested lists by default, and then style them when the containing list item is hovered over:

#navbar li ul {
	display: none;  }
#navbar li:hover ul, #navbar li.hover ul {
	position: absolute;
	display: inline;
	left: 0;
	width: 100%;
	margin: 0;
	padding: 0; }

The code above is the bit that really makes most of this magic work, so I’ll explain the important parts in some detail. First, because IE6 doesn’t support hover states on anything other than anchor tags, we’re writing our rules to account for the hover state and a hover class. This class is applied to elements when they’re being hovered over, using an ingenious little bit of JavaScript (which is explained in this previous dropdown menu tutorial).

Next up, we’re absolutely positioning our nested lists and using the “left” property to move the list to the left-most side. This isn’t moving the list to the left-most side of the screen, but instead the left-most side of its parent positioned element, which in this case happens to be the main unordered list that we positioned right at the start. As such, this trick relies of the whole list being positioned in some manner, even if it’s just relatively positioned and left in place.

The display: inline rule is a little more complicated. So much so, I don’t even completely understand what it’s doing. What I do know is, without that rule, the list items in the submenus simply don’t show up whatsoever in any major browser. I think it has something to do with the fact that the containing elements are floated (which we’ll get to in a bit), but I can’t prove that. If anyone has any better insight into the technical aspect, please let me know in the comments.

Lastly, the width: 100% rule is somewhat important. It’s preventing the unordered list from collapsing down to a smaller size in certain browsers. Specifically, without setting this width specified, the nested list sometimes collapses to the size of its “containing” list item (even though it’s absolutely positioned and therefore technically no longer contained). Note that older versions of Opera don’t deal well with the 100% width… if you want it to work on older versions, you’ll need to specify a width according to a definite size (such as pixels). However, the most recent version of Opera (9.27) handles it fine, and I get the impression that Opera users tend to upgrade more frequently than, say, IE users.

Finally, we just float the elements left (to put them in a nice horizontal row), and give them some colors:

#navbar li:hover li, #navbar li.hover li {
	float: left; }
#navbar li:hover li a, #navbar li.hover li a {
	color: #000; }
#navbar li li a:hover {
	color: #357; }

And that’s it! You can see a working example here. This has been tested and works fine in IE 6+, Firefox 2, Safari (Mac and PC), and Opera 9.27.

The only portion of the mockup I wasn’t quite able to duplicate was a way to keep the primary menu item highlighted when the submenu was in use: because the nested list is absolutely positioned, the browser doesn’t seem to consider them a matched set any longer (except, it seems, in terms of default width). If anyone has a solution to this bit, I would love to hear about it!

Thanks to Andrea for inspiring a hopefully useful tutorial! And if you ever have a CSS-related question that you think might make a good article here, don’t hesitate to send me a message, either via my contact page or on Twitter. I can’t guarantee I’ll use every question posed, but I’ll do what I can as time and situation allow.