Need help with a css site

[icehole]

I am building a site for a friend. The template I am using have 4 "boxes" and I need 5. I want the 5th centered below the other 4 but no amount of adding <align="center"> will get it centered. Any help would be appreciated.

 

[modi123]

Setting a size, and margin-left and margin-right to auto should center it to the larger div.

Ex:

<div style="width:200px;">
    <div style="float: left; display: block; position: relative;">
        <div style="width: 100px; height: 100px; float: left; background-color: red;">asdf</div>
        <div style="width: 100px; height: 100px; float: left; background-color: green;">asdf</div>
        <span style="clear:both;"></span>
    </div>


    <div style="clear: both; float: left; display: block; position: relative;">
        <div style="width: 100px; height: 100px; float: left; background-color: blue;">asdf</div>
        <div style="width: 100px; height: 100px; float: left; background-color: purple;">asdf</div>
    </div>
    <div style="clear: both; display: block; position: relative; width: 100px; height: 100px; background-color:yellow;margin-left:auto; margin-right:auto;"></div>
</div>