Css print control other than page-break-after & page-break-before

I'm designing a web interface that will print barcodes on an Avery sheet of labels. What's the best route for making sure everything lines up exactly on every label (would using physical measurements such as inches or centimeters help?) and more importantly - how can I ensure that each set of labels resides on its own page without bleeding into another page?I'm designing a web interface that will print b