function windowHeight()
{
  if (typeof(window.innerHeight) == 'number' ) {
    return window.innerHeight;
  } else if (document.documentElement &&
      document.documentElement.clientHeight) {
    return document.documentElement.clientHeight;
  } else if (document.body && document.body.clientHeight) {
    return document.body.clientHeight;
  }
}

function resizePortfolio ()
{
  var portfolio = document.getElementById('portfolio');
  if (portfolio) {
    height = windowHeight() - 270;
    if (height < 430) {
      height = 430;
    }
    portfolio.style.height = height + "px";
  }
}

window.onload = resizePortfolio;
window.onresize = resizePortfolio;