Yesturday I received 3 clicks on my one site equaling $1.97, and today, same site 3 clicks equals $0.08, Why?
It depends on the postion where ads have been clicked. Even in a banner ( 160x600 ), the ads which are on the top pay more than other ads. Also, your CPC depends on the amount advertisers have bid for a particular keyword.
I've seen that same thing happen on a wedding niche site. Huge swings in income depending on day, time of year, etc.