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

preload('communiques_on','/images/communiques_on.gif');
preload('communiques_off','/images/communiques_off.gif');

preload('letters_on','/images/letters_on.gif');
preload('letters_off','/images/letters_off.gif');

preload('speeches_on','/images/speeches_on.gif');
preload('speeches_off','/images/speeches_off.gif');

preload('subscribe_on','/images/subscribe_on.gif');
preload('subscribe_off','/images/subscribe_off.gif');	

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