Hi! Sorry for taking a while to reply. You didn't miss anything, technically, the width-height values were just mixed up a bit; in the code you gave me the background image width and the white bar width/height got switched. The inner div code has the values for the white bar, while the outer div code has the values for the background image.

Here's a quick fix:
<center><table style="font-family:impact; font-size:1.4em;letter-spacing:3pt;text-transform:uppercase;"><tr><td width="400px" style="align:center;"><div style="height: 225px; align: float; background: url(http://24.media.tumblr.com/7ac7516294663ed797da4d0a0a2ab502/tumblr_mj2gsqgOVZ1qgiou0o1_400.gif); background-position: center;"><div style="height: 25px; width: 400px; background: #eee; position: relative; top: 35px; opacity: 0.8;">mirror universe</div></div></td></tr></table>