Usually you know the page width in range units because you define them when creating the blueprint-css file ... so you can do something like this ... "span-x" is the segment width or page in units range measurements ... the "left" floats to the left, and the "right" floats to the right ... two cancel and center the div.
<body> <div class="container"> ... other stuff ... <div class="span-x right left last">center me</div> </div> </body>
source share