450)=450">

当我们经常发微博发图片时，你知道其中图片链接的奥秘吗。

450)=450"> 全文听写。
450)=450"> 为了六级，为了英语的提高，大家一定要耐心听写喔~~~

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点我回顾上一期【六级听力室】2010年12月真题短文2(1/2)
Why do "deleted" photos stick around so long? The problem relates to the way data is stored on large websites: While your personal computer only keeps one copy of a file, large-scale services like Facebook rely on what are called content delivery networks to manage data and distribution. It's a complex system wherein data is copied to multiple intermediate devices, usually to speed up access to files when millions of people are trying to access the service at the same time. But because changes aren't reflected across the content delivery networks immediately, ghost copies of files tend to linger for days or weeks. 　　In the case of Facebook, the company says data may hang around until the URL in question is reused, which is usually "after a short period of time", though obviously that time can vary considerably.