Multiple clicks on Adwords/Yahoo/MSN ads

[yougottakickalittle]

I'm rather new to the pay-per-click advertising game. But about a month ago I began purchasing ads on Yahoo and MSN's ad centers to promote my site. I plan to use Google's Adwords if these other campaigns show promise.

The problem I've noticed is multiple clicks, within a few seconds or a few minutes of each other, coming from the same refering link and logging the same IP address as the "clicker" of the ad.

What I'm curious about is, am I being double or triple charged when these multiple clicks from one user come through the same ad? I can't find any sort of discussion of this topic on MSN, Yahoo or Google.

If so, is there any way to prevent it? I have a very thin profit margin as it is, and paying extra for advertising would cut deeply into the meager profit I'm earning now.

Thanks for your help!

[yougottakickalittle]

I should clarify that I've found 15 instances of DIFFERENT users clicking on ads multiple times in the last three days. These are not all one user, but 15 different users who clicked on my ads twice or three times within one or two minutes (sometimes less).

[Traffic Master]

I don't think there is any way of preventing this. It's pay-per-click, so, you are charged for every click.