I want to know about cached pages that most of the search engines maintain even after crawling the website through 'robots'/'spiders'. I thought that these are not permanently archived. I also believed that the search engines regularly crawl the web to know if there are any pages that have been removed. With this, the pages would no longer appear, even as a cached page. Please tell me if my understanding is accurate. It would be great if you can help me know how search engine caching works. I am also looking forward to know the time period of web cache. I had read that the pages are cached for five years. Is that right?