How can an advertiser know how many people have a web page that their ad is on, if the web site owner is using

Question

Yahoo for web hosting?

Answer 1

Either of two ways:

1 - If the advertiser uses an ad server that allows the advertiser to login and check their real time stats (ad impressions, clicks, etc). Examples include OpenX http://www.openx.com or Google Admanager http://www.google.com/admanager

2 - If the advertiser uses a tracking code in their click through URL and how powerful their tracking software is (most only tracks click throughs)