title: ASP.Net codebehind - get google paid advert info
body: <p>I have an ecommerce site written in asp.net. Is there any way from my site code to see when a user was referred to my site from a paid google ad? Note that this should work on any page - not just the search landing page.</p>
  
  <p>[More detail - I can see in google analytics that 20%+ of paid click traffic eventually hits my 'register' page, but then only a small portion actually successfully registers. I want to check how many of these are failing the Captcha check, and hence are likely to be bots rather than real traffic.]</p>