function preload(imgObj,imgSrc) 
{
   eval(imgObj+' = new Image()')
   eval(imgObj+'.src = "'+imgSrc+'"')
}

preload('kyoto_on','/images/kyoto_on.gif');
preload('kyoto_off','/images/kyoto_off.gif');

preload('sustain_dev_on','/images/sustain_dev_on.gif');
preload('sustain_dev_off','/images/sustain_dev_off.gif');

preload('trade_on','/images/trade_on.gif');
preload('trade_off','/images/trade_off.gif');

preload('env_lead_on','/images/env_lead_on.gif');
preload('env_lead_off','/images/env_lead_off.gif');

preload('improving_on','/images/improving_on.gif');
preload('improving_off','/images/improving_off.gif');	

function img_toggle( imgName, mode ) 
{
   if( document.images ) 
   {
      document[ imgName ].src = eval( imgName + "_" + mode + ".src" );
   }
}