How do I distribute items horizontally with CSS?

You can do what you are after using inline-block, pseudo-elements and text-align: justify;, but it will only work in IE8 and above.

Here is the code:

<!-- HTML -->

<ul>
    <li>List Item 1</li>
    <li>List Item 2</li>
    <li>List Item 3</li>
    <li>List Item 4</li>
</ul>

---

​
/* CSS */

ul {
    text-align: justify;
}
ul:after {
    content: '';
    display: inline-block;
    width: 100%;
}
ul:before {
    content: '';
    display: block;
    margin-top: -1.25em;
}
li {
    display: inline-block;
    margin-right: -.25em;
    position: relative;
    top: 1.25em;
}

Live demo: http://jsfiddle.net/joshnh/UX9GU/ ​

As an addition to joshnh answer, if anyone has the same issue:

Watch out: text-align: justify; needs a space after every display: inline-block; element to work. Otherwise the elements are treated as one word and will not distribute horizontally.

So this won't work:

<!-- HTML -->
<ul><li>Item 1<li><li>Item 2<li><li>Item 3<li><li>Item 4<li></ul>

But this will:

<!-- HTML -->
<ul>
  <li>Item 1<li>
  <li>Item 2<li>
  <li>Item 3<li>
  <li>Item 4<li>
</ul>

I just had this issue because we are minifying our HTML-Markup and the minifier puts everything in one line.

There is an clean solution:

http://radiatingstar.com/distribute-divs-images-equaly-line

#container {
    text-align: justify;
}
#container > div {
    width: 100px; /* Declare your value. Can be in relative units. */
    display: inline-block;
    vertical-align: top;
}
#container:after {
    content: "";
    width: 100%;
    display: inline-block;
}