I have searched for an answer, but in vain. There are many reports about Adsense ads not showing up in different browsers, in my case it's Chrome. I implement adsense code within iframe tag, but this seems not a problem, because I build an experimental pages both with and without iframe (or together in one page), Chrome displays both correctly. My website is built on Microsoft Office Live for small business, its free hosting, a lot of restrictions. for example it will append a 'defer=defer' attribute to the adsense code.