I have a weird problem going on not sure how to fix it. i have a site thats showing PSA When i look at my site with www. it shows PSA When i look at it without It Shows up just fine. also its only the homepage. all internal pages are fine. I have other sites with Same amount of content and ads are displaying just fine. So that rules out lack of content. Hopefully i can get this cleared up. Thanks everyone. If anyone is interested i will send a PM with the site details for a better understanding..
when u get ad code there is an option , show public service ads OR fill space with color OR alternate url . if u will use this option then u will not get PSA ads.
I used to have this problem too, it's a problem of keywords. Just try to add the ad code in a place near to the contents or at least keywords and it should be fine.