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

preload('education_on','/images/education_on.gif');
preload('education_off','/images/education_off.gif');

preload('immigration_on','/images/immigration_on.gif');
preload('immigration_off','/images/immigration_off.gif');

preload('employment_ins_on','/images/employment_ins_on.gif');
preload('employment_ins_off','/images/employment_ins_off.gif');

preload('regional_dev_on','/images/regional_dev_on.gif');
preload('regional_dev_off','/images/regional_dev_off.gif');

preload('aboriginal_on','/images/aboriginal_on.gif');
preload('aboriginal_off','/images/aboriginal_off.gif');

preload('social_policy_on','/images/social_policy_on.gif');
preload('social_policy_off','/images/social_policy_off.gif');

preload('health_care_on','/images/health_care_on.gif');
preload('health_care_off','/images/health_care_off.gif');

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