if (document.images) {
  about = new Image();
  about.src = "../images/buttons/about_us.gif";
  about_on = new Image();
  about_on.src = "../images/buttons/about_us_on.gif";
  
  contact = new Image();
  contact.src = "../images/buttons/contact_us.gif";
  contact_on = new Image();
  contact_on.src = "../images/buttons/contact_us_on.gif";
  
  assessments = new Image();
  assessments.src = "../images/buttons/assessments.gif";
  assessments_on = new Image();
  assessments_on.src = "../images/buttons/assessments_on.gif";
  
  management_training = new Image();
  management_training.src = "../images/buttons/management_training.gif";
  management_training_on = new Image();
  management_training_on.src = "../images/buttons/management_training_on.gif";
  
  problem_solving = new Image();
  problem_solving.src = "../images/buttons/problem_solving.gif";
  problem_solving_on = new Image();
  problem_solving_on.src = "../images/buttons/problem_solving_on.gif";
  
  team_building = new Image();
  team_building.src = "../images/buttons/team_building.gif";
  team_building_on = new Image();
  team_building_on.src = "../images/buttons/team_building_on.gif";
  
  leadership_development = new Image();
  leadership_development.src = "../images/buttons/leadership_development.gif";
  leadership_development_on = new Image();
  leadership_development_on.src = "../images/buttons/leadership_development_on.gif";
  
  leadership_coaching = new Image();
  leadership_coaching.src = "../images/buttons/leadership_coaching.gif";
  leadership_coaching_on = new Image();
  leadership_coaching_on.src = "../images/buttons/leadership_coaching_on.gif";
  
  monthly_leadership_tips = new Image();
  monthly_leadership_tips.src = "../images/buttons/monthly_leadership_tips.gif";
  monthly_leadership_tips_on = new Image();
  monthly_leadership_tips_on.src = "../images/buttons/monthly_leadership_tips_on.gif";
}

function switchOn(imgName) {
    if (document.images) {
      document[imgName].src = eval(imgName + "_on.src");
    }
}
  
function switchOff(imgName) {
    if (document.images) {
      document[imgName].src = eval(imgName + ".src");
    }
}