Yes, there are definitely ways to verify the traffic, but you have to
have the website owner on board. I have various ideas below on what
you could do to confirm the traffic.
First, you could use a third party service such as
://www.google.com/adwords and advertise on the selected site
through that. The con is that Google will take a bit of a cut because
you are using their service, but the pro is that you would get
detailed information such as how many people click the link, how many
page views there are etc. Google Adwords has a feature that lets you
choose what websites you advertise on and gives you detailed
statistics. You would have to get the website publisher to sign up for
Google Adsense if this is the way you want to go (they can set their
prices). NOTE: In this case, you could potentially be outbid by other
Second, you could host the image on your own server. In this case,
your own server traffic would tell you how many times the picture was
loaded with detailed traffic information (including information on
geographic information, time of day people visit, etc.) When their
page loads, it would ask your server for the advertisement picture
which would allow you to record how many times it is asked for as well
as statistical information.
Third, you could check to see how many people click through or how
much attention you get from the advertising to see how effective it
is. You could for example, have a promotion where people get a deal or
discount if they mention the service (which would let you measure how
useful the advertising is). It is pointless to be paying for
advertising if you do not see direct proven benefits from it.
Fourth, you could ask for direct access to their traffic logs. If you
are paying a significant amount of money, and they are a small/medium
sized website... they should be able to give you this information.
As recommended by broken_form, Alexa rankings would also be a good
place to look: http://www.alexa.com/site/ds/top_sites?ts_mode=global&lang=none
Even if they are not listed there, you could ask them why and use this
as leverage to have them pursue one of the other options above.
Good luck and let me know if you require any clarification!