Well - I still have this problem, but it's clearly an intermittent one and perhaps less frequent lately. But just now I was looking at http://www.tuaw.com, where the lead story was "Apple lets kids play with iPads rather than iMacs". I visited that story, and when I swiped back to the home page, the lead story shown was "Deepworld launches Kickstarter Project to help fund a Mac bete," which was posted four days ago on April 23. I've closed the TUAW tab on my browser, reopened it and gone through the same steps again (this time using the back button), and again, going back opened the same page from four days earlier. When I refresh I get the correct page from today.
I have all current updates for Mac OSX 10.7.3, and see the same behavior (intermittently) on my iMac (21.5-inch, Mid 2010) and my older MacBook. I'll be surprised if the same page produces the same behavior on others' browsers though, since it would be unexpected for a problem like this to be related to the site rather than something internal to the browser -- just a guess.