There are a numbe of html errors on the page you should fix first before looking at the CSS. I know it isnt directly for the part thats not working, but they need fixing anyway.
First big one is:
<li class="PostCom"><a href="http://www.firsttimebuyersite.co.uk/site-information/first-time-buyer.html#respond" title="Comment on First Time Buyer">0 Comments</a></li>
<li class="PostCateg">Filed under: <a href="http://www.firsttimebuyersite.co.uk/category/site-information" title="View all posts in Site Information" rel="category tag">Site Information</a></li>
They havent got <ul></ul> wrapped around them! This is repeated many times through the page.
Some of the urls in the javascript are invalid:
<script language='javascript' src='http://www2.smart-quotes.com/NewMedia/NewMedia.aspx?id=1704&ctc=1135&src=1430&lnk=203&cmpg=&web=&brn=606'></script>
Example:
Incorrect : <a href="
http://www.domain.com/cgi?x=123&y=456">
Correct: <a href="
http://www.domain.com/cgi?x=123&y=456">
They also need a type attribute - 'text/javascript'. Language attribute is deprecated.
Try changing the CSS to:
.PostDate { text-align: center; margin: 0px; position: absolute; top: 0px; left: 1.5em; background: url(images/PostHead.gif) repeat-x bottom; width: 2em;}