Lenovo B40, Windows 10 problem?

I was listening to music on YouTube, and I hit a button on the keyboard, no idea what it was… Anyway, the video sound slowed down and the page went blank and now when I try to go any site, it's just blank and says "this page is having a problem loading"! What did I do and how do I fix it?

Added (1). Also, the Internet is connected.

Anytime you run into difficulties, the first thing to do is RESTART the computer. 95% of the time is clears the problem