Why do these bars exist?

webpage
so, i just strted learning html and css and im trying to insert a bf image for the while page, but i keep getting these bars np matter if i try to style it in a css page or the index html page. any idea why?

enter image description here

this is what i tried. I tried to do it in the index file and the css file but these bars keep appearing that interfere with the message. please help!