I see we’re still up, even after the asifa. 😉
Brech: The issue with entering a store and asking for help when you have no intention of buying is both onaas d’varim and ona’as mamon. The former because you get his hopes up and the latter because you are potentially taking him away from a customer who would buy. With that background in place, we can answer your questions. I’m going to take them in reverse order.
1-If there is an issur, if you do click it are you liable to repay the advertiser for his PPC cost incurred?
No. Even if there were an issur we rule (no source yet. mechon mamre doesn’t have shulchan aruch :/) that you are not chayav for this kind of onah. Which brings us back to your first question.
2-Is it halachicly permissible to click on an advertisement on a webpage, if you know (with certainty) in advance that you will not purchase the product being advertised for sale?
Yes. The ads go up with the understanding that they are just that — advertisements. The pay-per-click is an advertising fee, not a sales commission. The advertiser knows that not every click will generate a sale. He pays because each click has a chance of being a sale. In off line terms, the ppc fee is for getting you into the store, not for talking to you about merchandise.
PS Please don’t knock brech. People here are very understanding of someone who has far-fetched shailos in Orach Chayyim or Yoreh Deah. He’s going the extra mile to be ethical in Choshen Mishpat; let’s help him out. (Especially those who have learned more of it. This means you Popa, yitayningwut, Sam2, 147, DY and anyone else qualified.)