Forum Moderators: martinibuster
1) If the Google Adsense algorithm has trouble locating targeted ads for your pages, it may show PSA's.
2) If your pages contain stop-words, or words that may violate the Google Adsense, TOS, PSA's will be shown.
3) Also, if the Google Adsense network is experiencing problems...(ie. system maintenance, upgrades, etc.)... you may see PSA's.