Does anyone know why the text block div isn't centering? (Horizontally)

www.sheffieldfurniture .com/stickleysale/

Also, what have you guys found to be the best way to diagnose these types of problems? I find Firebug or Chrome developer tools to be a great way to dig into issues but what do you do when it's an IE6 issue?! Thanks for any help anyone can give!