function toggleCaseStudy( project_id )
{
  var d = document;
  var project_img = d.getElementById('portfolio_' + project_id);
  var imgOn = new Image();
  imgOn.src = 'images/portfolio/' + project_id + '_on.jpg';
  var imgOff = new Image();
  imgOff.src = 'images/portfolio/' + project_id + '_off.jpg';
  var link = d.getElementById('link_' + project_id);
  
  if (project_img.src == imgOn.src)
  {
    project_img.src = imgOff.src;
    link.style.color = '#a44532';
  }
  else
  {
    project_img.src = imgOn.src;
    link.style.color = '#373838';
  }
  
  return 1;
}