Center multiple divs in another div?

Here's an alternate method if you can use an extra div:

<div class = "container">
  <div class="centerwrapper">
    <div class = "square">...</div>
    <div class = "square">...</div>
    <div class = "square">...</div>
    <div class = "square">...</div>
  </div>
</div>

<style>
    .square
    {
        float: left;
        margin:1pt;
        width:72pt;
        height:72pt;
    }
    .container
    {
        text-align:center;
        width:450pt;
        height: 80pt;
    }
    .centerwrapper
    {
       margin: auto;
       width: 302pt;
    }
</style>

Also, make sure you have a closing quote on your <div class = "container"> there. The code you pasted is missing one.

Because you don't know the number of divs you have, you should use

text-align:center on the outer div

display:inline-block on then inner div

http://jsfiddle.net/edi9999/yv2WY/

HTML

<div class = "container">
    <div class = "square">John</div>
    <div class = "square">Mary</div>
    <div class = "square">Doe</div>
    <div class = "square">Jane</div>
</div>

CSS

.square
{
    margin:1px;
    width:20%;
    text-align:left;
    border: 1px solid gray;
    display:inline-block;    
}
.container
{
    text-align:center;
    width:100%;
    height: 80pt;
    border: 1px solid black;
}

As #RwL say, using <span> works, here a sample code, tested on IE6/8, Chrome, Safari, Firefox:

CSS

<style type="text/css">
    /* borders and width are optional, just added to improve visualization */
    .parent
    {
        text-align:center;
        display: block;
        border: 1px solid red;
    }
    .child
    {
        display: inline-block;
        border: 1px solid black;
        width: 100px;
    }
</style>

HTML

<span class="parent">
    <span class="child">
        A
    </span>
    <span class="child">
        B
    </span>
</span> 

Instead of floating the .square divs, give them display: inline-block. This might be dodgy in Firefox 3.0.x but I believe inline-block is fully supported in 3.5.x.