As SoopahMan said, you need to apply centering in two ways when using CSS. Furthermore, for IE if you say something like <div align=center>, that centers everything inside the div so you then need to add align=left inside the div.
But back to basic centering. For objects like tables the correct method is to apply margin-left:auto; margin-right:auto; to the object being centered. However, this doesnt work in IE so you also need to apply either or text-align:center; around the table being centered.
Any problem with HTML can be discussed here.