Quite self explanatory, I have seen quite a few websites with more than 3 ad placements from Google on one page. How can this be done?
Premium publishers? Also, you can put 3 regular ads and 3 link ads if that might be what you're seeing?
I've noticed with my sites that if I put more than 3 of one type then none will show. This might help you out with testing op, good luck.
Link ads are just a single word (or few-word phrase) The regular adsense units are the ones with the description and like you see a the very top right hand corner of this webpage.
For the very limited content that there is, there are already WAY TOO MANY ADS on that webpage as it is! Three of the five ads are link units, though, so nothing is being violated other than placing ads on a page with virtually no content.
Search around here, the question has been asked and answered MANY times. Here you go, the first one's free: http://forums.digitalpoint.com/search.php?searchid=19287964