The idea is correct, but first thing you should care of is the width. First of all, the element may take the whole width of the page or parent element. Say, you can inherit it from your more general table style. In this case, you center, but you need a room to center in. So, make sure the element to be centered is limited in width. It could be defined by content of the table (default), or you can use percentage.
Please see:
http://webdesign.about.com/od/beginningcss/a/aa012207.htm.
—SA
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