Centering tables on different size monitors

I am having a problem centering three tables across my webpage and having it stay centered on all size monitors. My monitor is 17" and the tables are perfectly centered on my monitor, but they all shift to the left on a 22" wide monitor. Here is my Coding:

         table.heading {width: 300px; height: 300px; background-color:#FFFF99;

         table.heading {margin: 0px}
#heading1 {position: absolute; left: 135px; top: 350px}
#heading2 {position: absolute; left: 485px; top: 350px}
#heading3 {position: absolute; left: 835px; top: 350px}

         <div id="heading1" class="heading">
<table class= "heading">

Any help woul be appreciated…thanks ajzammy.

Do you have a demo of this in action as it’s kind of hard to point the finger without been able to test it.