How do I get the max-width of a TD

How do I get the max-width of a TD

I have a TD that is styled with a class that gives it a max-width as follows:
  1. #newDivCenter {
        background-color: yellow;
        text-align: center;
        min-width:788px;
        max-width:840px;
    }
When I try to retrieve that max-width, I fail.  I tried plain JavaScript:
  1.  var newDivCenter = document.getElementById("newDivCenter");
      alert(newDivCenter.style.maxWidth);
but that failed, so would jQuery work instead?  How would I try it in jQuery? 
So far, it fails on a TD, and also on a TABLE element (I tried both)