Why your blog showing Public Service Ads?
Recheck your Adsense code was inserted properly on your webpage. Do no attempt to modify the code in any way, as it is against their terms of service. Adsense gives enough options to costumize ad colours and sizes to suit your site. USe only the official code available from their site.
There may not be any ads configured to show in your region. Lets say that these ads may be working in United States, but maybe showing PSA is Zambia. This is because Google Adwords payers can select regions where to display their ads, where they believe their target surfers are. After all why should an eye surgeon in US want to promote his service in Zambia? Try using the Google Adsense Preview Tool which helps to determine probable ads in different regions.
Your site maybe using a robots.txt file, which will may not be properly set up and prevent the AdSense crawler from crawling your web pages. Add the following two lines to the top of your robots.txt file:User-agent: Mediapartners-Google* Disallow:
Your page may contain objectionable content. This may be against Google Adsense policies. If you feel your page has no such content, then look for any objectionable keywords or phrases which may be present accidentaly. Removing such content can cause PSA’s to dissapear.
Frames may occasionaly cause difficult in indexing your page. Always remember to tick the Framed page checkbox from the Ad layout code page when generating your ad code. Similarly IFRAME’s also prevent effective indexing and cause PSA’s
Reduce your filter blocked urls. This feature is in place to allow you to block competitors ads from showing on your pages. If you block too many such urls, there may not be any advertisers left to display ads.
Remove session ID’s from urls - they changes every time a different user views a page, and the URL will not be in the indexed everytime.
Google may take time to crawl your site. Although most of the times the ads show immediately, at times it takes upto 48-72 hours for google to assess the content of newly created webpage. This usually occurs if your site has not been indexed before by Google. The time is reduced on newer pages of a site already running adsense. Google claims the ads will get better and more focussed to your pages with time.
Related articles: How to avoid Adsense PSA