they could be ads due to some game or app that you downloaded from the market. I get these all the time, and they are annoying. they are kind of like spam emails that you get on your pc, you have to figure out how to unsubscribe to them, or figure out what game (it's usually a specific company) invited the "spam" and delete the game. I did some googling about a month ago on this, and there's an app out there that will actually let you know which apps are allowing ads, and IF you can delete (opt out) the ads. it's called ad network detector, and it works pretty good. I opted out of 4 "ads", but some games/apps won't allow you to do it. for example, Go launcher has parts of it that allow these, so I have to either delete Go laucncher, or deal with the annoying "ads". airpush is one of the biggest offenders, and I used their "opt out" app, and I still get them. so, I'm just dealing with them. good luck on your research.