css - how to evenly distribute elements in a div next to each other?

Question

This is meant for a menu.
For example I have a div element with 3 spans in it, all of which have some margin, max-width and float (left or right).
It is positioned starting from the left side and goes like this:
[[span1][span2][span3] - lots of free space here].
I want to make it even out like this:
[[span1] - space - [span2] - space - [span3]]
How can I do this using CSS? I kinda doubt it is not possible.
Note that I want it to keep the same style when I add or remove a menu item.
HTML:

<div id="menu">
    <span class="menuitem"></span>
    <span class="menuitem"></span>
    <span class="menuitem"></span>
</div>

CSS:

#menu {
    ...
    width:800px;
}
.menuitem {
    display:block;
    float:left;
    margin-left:25px;
    position:relative;
    min-height:35px;
    max-width:125px;
    padding-bottom:10px;
    text-align:center;
}

Answer 1

In the 'old days' you'd use a table and your menu items would be evenly spaced without having to explicitly state the width for the number of items.

If it wasn't for IE 6 and 7 (if that is of concern) then you can do the same in CSS.

<div class="demo">
    <span>Span 1</span>
    <span>Span 2</span>
    <span>Span 3</span>
</div>

CSS:

div.demo {
    display: table;
    width: 100%;
    table-layout: fixed;    /* For cells of equal size */
}
div.demo span {
    display: table-cell;
    text-align: center;
}

Without having to adjust for the number of items.

Example without table-layout:fixed - the cells are evenly distributed across the full width, but they are not necessarily of equal size since their width is determined by their contents.

• http://jsfiddle.net/w3dx/ULQwf/

Example with table-layout:fixed - the cells are of equal size, regardless of their contents. (Thanks to @DavidHerse in comments for this addition.)

• http://jsfiddle.net/kqHWM/

If you want the first and last menu elements to be left and right justified, then you can add the following CSS:

div.demo span:first-child {
    text-align: left;
}
div.demo span:last-child {
    text-align: right;
}