<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
        "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html>
  <head>
    <style>
      div {background-color:#ccc; margin-bottom:4px}
      div * {vertical-align:text-bottom}
      div span {background-color:red}
      body { font-family: Monaco; }
    </style>
  </head>
  <body>
    <div>
      <span style="font-size:15px">small</span>
      <span style="font-size:30px">BIG</span>
    </div>
    <div style="line-height:100px">
      <span style="font-size:15px">small</span>
      <span style="font-size:30px">BIG</span>
    </div>
    <div style="height:100px">
      <span style="font-size:15px">small</span>
      <span style="font-size:30px">BIG</span>
    </div>
  </body>
</html>