var iversion = -1;

function version() 
{
  if (document.images)
    iversion = 3;
  return iversion;
}
version();
PImages = new Array();

function rollon(imgName) {
 if (3 <= iversion)
   document[imgName].src = PImages[imgName + "on"].src;
 return true;
}

function rolloff(imgName) {
 if (3 <= iversion)
    document[imgName].src = PImages[imgName + "off"].src;
 return false;
}

function preloadImages() { 
 if (3 <= iversion) {
  a = preloadImages.arguments;
  for(i=0; i < a.length; i+=2) {  
    PImages[a[i]+"off"]=new Image();
    PImages[a[i]+"off"].src = a[i+1]+"off.gif";
    PImages[a[i]+"on"]=new Image();
    PImages[a[i]+"on"].src = a[i+1]+"on.gif";
  }
 }
}