[Groxx]

Like this:

  #left{
    float:left;
    width:200px;
    margin-right: -200px;
  }
  #right{
    float:right;
    width:200px;
    margin-left: -200px;
  }
  #middle{
    float: left;
    margin-left: 200px;
    margin-right: 200px;
  }

People tend to avoid this relatively simple solution because of the double-left-margin bug in IE 5 & 6, but that's getting to be an excessively old set of browsers. And even then, it's usually fixed with a "display:inline;" on the ones with left margins.

edit: it's not an ideal solution, as it has those negative values which have to match the related positive ones. Which is solved with something like Sass or Less, because CSS lacks any "programming" abilities, which I see as its main failure. Even variables and simple math would be acceptable, but instead, nothing.

[Groxx]

Downvote? It's correct, and it's exactly what was asked for. Here's a Fiddle demonstrating it: http://jsfiddle.net/yBs5V/

[kerryfalk]

Or, to make it _really_ simple:

  <div class="column">1</div>
  <div class="column">2</div>
  <div class="column">3</div>

  div.column {
    margin: 10px;
    width: 200px;
    float: left;
    }

EDIT: Missed the key constraint, resizable center column. What I have above won't work for that, but shows that replacing tables isn't very difficult.

[yid]

Nope, not quite. Resize your window to less than 600px and see what happens.

[kerryfalk]

You can wrap the above in another div with a width of 660px or greater and it'll have the same effect as a table if the window width is less than the width of the columns (plus margins/padding).