function changeMyClass(element,firstClass,secondClass){
 if(element.className == firstClass){
   element.className = secondClass;
 }
 else{
   if(element.className == secondClass){
     element.className = firstClass;
   }
 }
}
if (document.images)
{
  pic1 = new Image(192,21);
  pic1.src = "/images/nav_bottom_blue.gif";
  pic2 = new Image(192,21);
  pic2.src = "/images/nav_bottom_yellow.gif";
  pic3 = new Image(192,21);
  pic3.src = "/images/nav_top_blue.gif";
  pic4 = new Image(192,21);
  pic4.src = "/images/nav_top_yellow.gif";
}