Web site keeps popping up

A few weeks ago, I went to this website:

http://nimpekprg.com/download-youtube-videos-as-mp4/

And now, I cannot get rid of it. It opens when I first start CD.

If CD has been opened on my desk top for a few hours, it opens again in a new tab.

I’ve scanned for adware. I’ve scanned with Malwarebytes. They find nothing. I’ve looked in the registry.

WHY DOES THIS KEEP POPPING UP???