How do you embed a website to another one?

On my website, I want to embed another website into it, so that the two websites are exactly the same. I used the Iframe tag in HTML, although there was a weird border, and because Iframe only embeds, and not mirrors, there would just be a blank spot of 'white' on larger displays. So, I couldn't use that. I could try seeing if my domain host supports Mirroring and see if that works. Please tell me if there's another way.