<!DOCTYPE html> <html> <head> <title>background-position: top, bottom reference</title> <style type="text/css"> #outer { border: 1px solid black; width: 128px; height: 128px; } #inner1 { margin-left: 48px; /** 128px - 128px * 0.50 + 32px * 0.50 - 32px **/ margin-top: 0px; width: 32px; height: 32px; background-image: url(aqua-32x32.png); } #inner2 { margin-left: 48px; /** 128px - 32px - 32px **/ margin-top: 64px; /** 128px - 128px * 0.50 + 32px * 0.50 - 32px **/ width: 32px; height: 32px; background-image: url(aqua-32x32.png); } </style> </head> <body> <div id="outer"><div id="inner1"></div><div id="inner2"></div></div> </body> </html>