work-with-bfcache.js

// https://developer.mozilla.org/en-US/Firefox/Releases/1.5/Using_Firefox_1.5_caching

window.onpageshow = function(event) {
  if (event.persisted) {
    // the page is loaded from cache
  }
}

// in jQuery
$(window).bind("pageshow", function(event) {
  if (event.originalEvent.persisted) {
    // the page is loaded from cache
  }
});