Check whether the process needs to go on; the user might have decided to pageforward or backward, and it wouldn't do for the former page data to show up.
检查是否需要继续处理；用户可能决定向前或向后翻页，对于前面的页面数据不再处理。
2
The pageforward/back buttons, the most-used buttons on a Kindle, have moved from the screen bezel to the sides of the device, which is a little more awkward, and feel a little mushier.
Kindle最常用的“前进/后退“按钮从屏幕的边框移到了侧边，用起来不舒服，感觉上也别扭。
3
The page cache stores the entire page as a single entity, so when shuffling between pages using the back and forward functions of the browser the page loads immediately from the cache.