if (document.images)
{  
homeon = new Image ;
homeoff = new Image ;  
mapon = new Image ;
mapoff = new Image ;
mailon = new Image ;
mailoff = new Image ;
 
homeon.src = "i/home_on.gif";
homeoff.src = "i/home_off.gif";
mapon.src = "i/map_on.gif";
mapoff.src = "i/map_off.gif";
mailon.src = "i/mail_on.gif";
mailoff.src = "i/mail_off.gif";
}
function img_act(imgName)
{
 if (document.images)
 {  
  imgOn = eval (imgName + "on.src");
  document [imgName].src = imgOn;
 }
}
 
function img_inact(imgName)
{
 if (document.images)
 {  
  imgOff = eval(imgName + "off.src");
  document [imgName].src = imgOff;
 }
}