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Google has similar functionality baked into it's Survey tool: http://www.google.com/insights/consumersurveys/website_owners so you could look at how they handle it / recommend setting their own version up and then be pretty confident that you're version (whatever it is--just using a pop up survey as an example) is working within their guidelines. (Here's their example: http://www.google.com/insights/consumersurveys/websat_example) Different regional images shouldn't be a problem either. Your experience might vary on the last question. With some sites and exit survey seems to work best while others lend themselves to timed or first landing.  You could split test that though and come up with an answer pretty quickly.  Cheers!