Strange Centering Issue

I have a main table that is 740x726 in my document. I want it centered, absolutely. When I align the table to center or wrap the table in <center> tags it centers, but not absolutely. When the page is refreshed it jumps a pixel or two back to the right where it should be. I have a centered background image that tiles vertically to give the illusion of side bars or borders per say. I can tell the difference when I open the page, and the main table is off center a little, then I refresh and it slips to its correct spot. How can I elminiate this slight error? I thought about using CSS but would not be sure how to write that.