The only time I've ever encountered that was when it popped up in a new tab, and I went back to the previous tab. Do you have it set so that it welcomes you on the same tab, and not a new one?

I can't think of anything else you should have to do for a Mac. Do you have anything set in preferences for how long your browser should remember where you have been? Not sure if that is an issue? I use Firefox exclusively, but that shouldn't be an issue with what you use, just preferences.

What kind of laptop from Apple did you get?! I have a MacBook.