Just learned about this now. There's a Google AdSense Preview Tool, which only works with Internet Explorer so that you can see or preview what type of ads are shown to your site's user located in a particular geographic location. As you may already know, Google advertisers can choose the geographic locations where their ads can be shown. In other words, the ads shown to the user is determined by his or her I.P. address.

Related to this, I have read somewhere that ads served to U.S. users have a higher payout than ads served in the Philippines. Based on my experience from AdSense clicks on my international website WriteLit.com and my local website FilipinoWriter.com, this seems to be true. Usually, an AdSense click on WriteLit.com is worth three FilipinoWriter.com AdSense clicks. I am therefore looking to create more websites and posts which have a more international appeal to see if I can earn more.