Q: When building a affiliate website when they click on the buy now button is best to open the page in new tab/Windows or just go straight the merchant website?
A: Part of this comes down to personal preference.
I set my affiliate links to go direct, instead of launching a new tab or browser windows.
In my opinion, it’s a bad user experience to launch new tabs or browser windows.
However, I would encourage you to test it with your audience, because all audiences, niches, etc. vary.
Try it both ways and see which yields the best results for you.