PrintnPost.com FAQ

You can use the printnpost.com url to signup for adsense but as a heads up, sometimes google has declined the url depending on who does the review. Since adsense assumes you own the website where the adsense code will appear they sometime check the domain(url) registeration to see if it matches what you submit. 

If they reject you, simply setup an account at blogger.com which google happens to own and submit the url they give you.(they never reject thier own urls) Or you can purchase a domain for your self at www.o2sdomains.com and submit that url. you can then simply fwd the url address to your author page.