// images preload
function imgPreload() {
   // section hover
   var img1 = new Image; img1.src = 'images/index_section_2.gif';

   // section labels
   var img2 = new Image; img2.src = 'images/label_1a.png';
   var img3 = new Image; img3.src = 'images/label_2a.png';
   var img4 = new Image; img4.src = 'images/label_3a.png';
   var img5 = new Image; img5.src = 'images/label_4a.png';
}

function setCssClass(id, css) {
   document.getElementById(id).className = css;
}

function swapImage(id, name) {
   document.getElementById(id).src = 'images/' + name;
}