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

preload('corp_gov_on','/images/corp_gov_on.gif');
preload('corp_gov_off','/images/corp_gov_off.gif');	

preload('corp_cit_on','/images/corp_cit_on.gif');
preload('corp_cit_off','/images/corp_cit_off.gif');	

preload('national_on','/images/national_on.gif');
preload('national_off','/images/national_off.gif');	

preload('fed_prov_on','/images/fed_prov_on.gif');
preload('fed_prov_off','/images/fed_prov_off.gif');	

preload('parli_on','/images/parli_on.gif');
preload('parli_off','/images/parli_off.gif');	

preload('political_on','/images/political_on.gif');
preload('political_off','/images/political_off.gif');	

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