/*
 * Sets the src property of an image.
 *
 * image: the image id.
 * src: the image's src value.
 */
function rollover(id, src) {
  var image = document.getElementById(id);
  if (image != null)
    image.src = src;
}

/*
 * Sets the display property of an object.
 *
 * id: the object's id.
 * style: the value to set the display property to.
 */
function setDisplay(id, style) {
  var obj = document.getElementById(id);
  if (obj != null)
    obj.style.display = style;
}

/*
 * Sets the html displayed within an element.
 *
 * id: the element id.
 * html: the html to display in the element.
 */
function setHTML(id, html) {
  var obj = document.getElementById(id);
  if (obj != null)
    obj.innerHTML = html;
}