CSS different in FF and IE

I saw a nice effect on a site whilst browsing, which uses CSS to displays a date which looks a bit like a page-a-day calendar.

i have tried to emulate it, and whilst the effect looks ok in FF, it doesn't look as good in IE.

page is here news.php

css class is as follows...

.date {
float: left;
width: 70px;
padding: 1px;
background: #990000;
border: 1px solid #990000;
text-align: center;
font-size: 12px;
color: #fff;
line-height: 16px;
font-family: Verdana, Geneva, sans-serif;
margin: 0 15px 15px 0;
padding: 0 0 0 0;
}
.date x {
display: block;
padding: 1px;
background: #fff;
font-size: 14px;
font-weight: bold;
color: #CC0000;
}
.date b {
display: block;
padding: 5px;
background: #fff;
font-size: 20px;
font-weight: bold;
color: #000;
}

Have I made a glaring error with this ?, grateful for any advice