One way (although not super reliable) is to look at the website's Last Modified header. Click here and enter the website, and then scroll down to the Last Modified header, which shows a timestamp.

The problem with it, is a lot of sites, like GeekDrop, or FaceBook, etc. are constantly updating that last modified header, so trying to view one person's page for example, won't work out.

There are other ways though. You can download the Firefox addon called Update Scanner and set it to watch the page for you. There's also a separate program that does the same thing, called Webmon.

Edit: Weird, the webmon link gets redirected. Try Googles cache instead if it happens to you.

Good luck