Yes, that got me going. The following:

class { display: block; font-size: xx-large;   }
signature { display: block; font-size: large; margin-top: 1em }
P { display: block;  font-size: medium; font-family: georgia, bookman, serif; margin-top: 1em }

was enough to get readable output in a browser from my posted XML file.

It seems that IE doesn't handle the :before pseudo-tag.