OK, OK, I bite myself in foot. I explain...
I have client with two websites, both originally setup as frames site. I know css is better, but I'm not responsable for rebuilding whole sites to accomodate shopping carts.
I see error of my way using _blank in code. I see this is not what I mean first time I test. I change to correct _parent. This is for busting-out of frame. To do this here allows store customer to be warm and fuzzy with all the nice ssl bells happy.
To continue the flow, when the sucess page is called and the customer is back on the site, along with the thank-you-for-your-purchace message, it also say in big friendly letters, please click here to return to the main website. This click take then right back to where they need to be. And if not, is all ok cuz sale has gone through anyway.
I check with several browsers that all works well and that all backend and emails are set right.
Is reasonable workaround for having to integrate into site where frames are not yours able to control.
To use your builders anology, I do not see sense in tearing down whole house to add a new porch. New porch has to be made to work into existing structure.
Anyway, having to take long quiet walk through code to see how to do this make me better zenner in long run.
I hope not to peeoff too many people here. Someday I may REALLY need help :)
Kiddo