How to remove web pages from the dock

I want to remove the webpage icon on the dock it's located on the right next to the trash bin. I don't know if I accidentally added it there or if it has always been there. It goes away when you're on it but when you minimize the window it appears. I've tried to remove it by dragging away but it just moved and didn't disappear. just wondering if I caused it or if it was always there.