Why do you need it invisible? So people don't click on it and lose traffic? I've seen lots of pages with a small .gif for the counter and with the text "don't click here, it's just a counter", although I don't know how "fair" it is to write that (i.e. if those counters allow it). But you can put an accurate counter on your page, even with a small pic or whatever image you want, leading to paysites that pay you weekly $25/3 day free trial with no deductions:
CE's Cash Count Program
You can track different pages. So, instead of paying for one, you get paid.
