this used to happen in Google Images a lot, still does sometimes.
one way this is done is when you click the link to a page, it directs you to an 'invisible' page that as soon as navigated to directs you to the desired page without you noticing. this means that when you click the back button you're not going to the page you were originally on when you clicked the link, but you're going to the page that was there for a fraction of a second that redirects you back to the same page. this means that one needs to click the back button a few times really fast to get out of it. sounds like what is happening.
obviously this isn't Newschooler's doings. Take note of what ads appear when this happens, it might be one of them? Also when it does happen check your browser history right away. There will probably be a page in there between the two pages you though you went between. post up the information to that page.