Despite my personal objections to using tables for layout, you need to apply the centering to the table and not to the container. The following will work in almost every browser:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
<table style="border:1px solid #000; width:500px;margin:1px auto;">
It is important to note that this type of style should be called from a linked file and not in the HTML and may be represented as follows:
border:1px solid #000;
Also you MUST declare the doctype or when IE is thrown into quirks mode it will not render the table as centered.
Now just so you know, there is no reason you can't use another div instead of a table to contain the page content. That being said, I am glad that you are making the move to better, more modern coding.
All the best,