function rollon() {
  if (window.event.srcElement.className == "Basic") {
     window.event.srcElement.className = "Highlight";
  }
}

document.onmouseover = rollon;

function rolloff() {
  if (window.event.srcElement.className == "Highlight") {
     window.event.srcElement.className = "Basic";
  }
}

document.onmouseout = rolloff;