Each clickable item should quickly tell the viewer what to expect. If your home page takes more than a few seconds to load, viewers will abandon you for a more user-friendly site and you most probably will lose that potential buyer forever. Flashing banner ads, especially those with no connection to your offering, will merely annoy your viewer. I implore you to keep them off the top of your home page. If you absolutely must have a banner ad, put it on the bottom or on an inside page where it won't be so intrusive.
Nothing annoys like a new window or a back-button redirect.
If I want to open a new window, I'll do it. Don't you try to force me. Most viewers are looking at your site with the intention of possibly buying from you, and if you destroy their path back to your home page, you may destroy the potential for a sale. The back button redirect is even more annoying. In short, sending the viewer to a new page when they want to go back is stupid.