if (document.images)
   {
	 homeOn= new Image(54,20);
     homeOn.src="images/home_on.gif"; 
	 	 
     agendaOn= new Image(60,20);
     agendaOn.src="images/agenda_on.gif"; 
     
     companiesOn= new Image(150,20); 
     companiesOn.src="images/companies_on.gif";
     
     speakersOn= new Image(69,20); 
     speakersOn.src="images/speakers_on.gif";
     
     
     
     
     homeOff= new Image(54,20);
     homeOff.src="images/home_off.gif";
     
     agendaOff= new Image(60,20);
     agendaOff.src="images/agenda_off.gif";
     
     companiesOff= new Image(150,20);
     companiesOff.src="images/companies_off.gif";
     
     speakersOff= new Image(69,20);
     speakersOff.src="images/speakers_off.gif";
     
   
     
   }

function lightup(imgName)
 {
   if (document.images)
    {
      imgOn=eval(imgName + "On.src");
      document[imgName].src= imgOn;
    }
 }

function turnoff(imgName)
 {
   if (document.images)
    {
      imgOff=eval(imgName + "Off.src");
      document[imgName].src= imgOff;
    }
 }