I read this excellent article on centering and as the comments are suspended, I thought I'd post about it instead.

I think the floater div position is inconsistent. In 'Which Method?' the floater is a closed tag above the content. In Method 3 the floater wraps the content.

Also a potential con for Method 3 is that you need to know the height of the content, where as you don't for Method 1.

I went with Method 1 as IE9 supports it, though for wider compatibility I should include the IEx hacks.