div {
  display: table;
  width: 144px;
  height: 115px;
}

div span {
  display: table-cell;
  vertical-align: middle;
  text-align: center;
}

.ie6 div, .ie7 div {
  padding-top: 3em;
  height: 8em;      
  voice-family: "\"}\"";
  voice-family: inherit;
  height: 4em;
}

.ie6 div span, .ie7 div span {
  margin-top:-0.5em;
  display:block;
}

vertical align in IE6-8, Firefox

CSS