Layout Issue

[4D1]

Hi Guys, I am still learning HTML & CSS, I am having an issue with my layout in IE & FF, I did have it working perfectly in IE and thought I would test it in FF, it seems my links accross the top are around 5px different in each browser so I have made them meet half way and the mailing list is spaced in FF, I have changed the images and been messing around with it for ages and cant get it to sit right in both browsers, can anyone identify the problem? also if anyone has any comments on the code could it be done better/cleaner? Thanks in advance

http://www.allthreads.co.uk

div.head {width: 890px;height: 100px;background-image: url('images/head_background.png');margin: auto;}table.buttons{float: right;margin-top: -2px;width: 700px;}td.images{text-align: center;font-family: arial;font-size: small;font-weight: bold;border-right: 1px solid black;}td.imageend{text-align: center;width: 220px;}img.logo{margin-left: 25px;margin-top: 3px;}div.holder{width: 890px;height: 700px;margin: auto;clear: top;}div.leftnav{height: 700px;width: 200px;border: 1px solid black;margin-top: 0px;margin-left: 0px;}div.graycell{background-color: #9999ff;width: 200px;height: 80px;float: top;}