On some websites, like CNN shown in the video above, when I hit "back" to return to the previous page, instead of getting the previous page I get a version of the previous page that's from some time in the past, as much as a day or so. I've also had this happen on sites like Reddit. Unless Apple included highly advanced tachyon-based time travel functionality in iOS 5, there's some problem between the web server, the cache, mobile Safari, and my eyes that's conspiring to give me pages from the past.
You get an older version of the web page you just left.
That gets Safari to render the page again. You can also clear the cache. That seems to alleviate the problem, at least for a while.
I haven't tried this in iOS 5.0.1 yet and it may well be fixed in that build, otherwise here's hoping Apple fixes it soon.