IIRC, Dani doesn't allow popups, or flyins, or anything obtrusive in her agreements with advertisers. I'd suggest sending her a screenshot when you get it again, because the advertiser may be in breach of contract.
It's actually a bit more complicated than that, Narue. I request of the networks that I work with to not allow popups, flyins, etc. Those networks then deal with ad agencies who in return deal with the marketing branches of the companies themselves or with other advertising agencies who deal with the marketing branches of the companies.
If an intrusive ad slips through the cracks, it is a semi-long process tracking down exactly where it is coming from and requesting a fix (a process that can take weeks as it travels through the hierarchy to those who designed the banners, and then back again). Thankfully this doesn't happen all too often.
I first noticed the HSBC ad day before yesterday. It is not meant to be so intrusive but is actually a bug in the ad code that appears to only affect IE (at least for me, it does). I began the process of trying to track down which network the ad is coming from, so I could inform them, when I realized that I stopped seeing it as of yesterday morning and no one commented on it all day long, so I was kinda hoping the problem would just go away itself. :) Guess not.