CSS display differences in I.E.

Hi, I’ve created a guestbook using WordPress here:

http://demulesca.net/?page_id=12

In Mozilla Firefox, if you view the comments they look perfect. However, when you switch to I.E., the borders of the comments change and the header for the individual comments becomes seperated from the rest of the content.

This is my CSS Code:

.commentacontainer {
padding: 0 1px 0 1px;
width: 662px;
background: #383838 url(images/commentabackground.gif) repeat-y;
}
.commentaleft {
float: left;
width: 93px;
background-color: #8f8f8f;
border-left: 1px solid #c4c4c4;
border-right: 1px solid #c4c4c4;
border-top: 0;
border-bottom: 0;
margin: 0 4px 0 0;
}
.commentaright {
float: right;
margin: 0 2px 0 0;
width: 559px;
background-color: #495a43;
border-right: 1px solid #859673;
border-left: 1px solid #859673;
border-top: 0;
border-bottom: 0;
}
.commentaheader {
width: 662px;
padding: 0;
background: #383838 url(images/commentaheaderbackground.gif) no-repeat;
height: 3px;
}
.commentafooter {
width: 662px;
padding: 0;
background: #383838 url(images/commentafooterbackground.gif) no-repeat;
height: 3px;
clear: both;
}

Can anyone help me?