Center alignment 1 February 2008

<style type="text/css">
.align_center
{
position: relative;
width: 100%;
}
.align_center:after
{
content: '';
display: block;
clear: both;
}
.align_center_to_left
{
position: relative;
right: 50%;
float: right;
}
.align_center_to_right
{
position: relative;
z-index: 1;
right: -50%;
}
</style>
<div class="align_center" style="border: 1px dashed red; color: red;">
Alignment with respect to this block
    <div class="align_center_to_left">
        <div class="align_center_to_right" style="margin: 1em 0; border: 1px dashed green; color: green;">
            Block width depending on line length
        </div>
    </div>
</div>