Well... there is nothing messed up with the website that can cause this problem. Really.
Of course I am trying to help you. The thing is: It is technically impossible this comes from the website. There just is no code for pop ups. And if there is no code this cannot happen without an outside source. I have checked it and asked many people (including programmers), just in case I am missing something. You can believe me there is no technical reason for this to happen. So my conclusion is it must be something on your computer. A virus, malware or maybe an old browser version with problematic add ons? Is your anti virus software up to date?
Edit: Okay, NOW I know who you are
. It seems like you used a different e-mail address for the donations, so that's why I was confused and asked for your name. I sent you an e-mail in September. Again I am very thankful for your support, but unfortunately I cannot fix the problem if its source is not on the website.
But I have an idea: Can you please make a screenshot of the pop ups which appear? This way I might see where the problem comes from (I still suspect a browser add on or virus because this is very common).
If you do not know how to make a screenshot I can help you with this. Which version of Windows (or OS X) are you using?
If you still have technical problems with the forum we can write e-mails. firstname.lastname@example.org
is my address.