intImage = 2;
function swapImage() {
switch (intImage) {
 case 1:
   document.getElementById('index_arrow').src = "http://www.twu556.org/images/shell/white_arrow.jpg"
   intImage = 2
   return(false);
case 2:
   document.getElementById('index_arrow').src = "http://www.twu556.org/images/shell/white_arrow_up.jpg"
   intImage = 1
   return(false);
 }
}