Style the HTML Body Element?

Tell us what’s happening:

where wrong?

Your code so far

body {
  background-color: black;

Your browser information:

Your Browser User Agent is: Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/64.0.3282.140 Safari/537.36.

Link to the challenge:

Does the style element have an opening tag as well as a closing tag?

thx,But not this problem,I know why I was wrong,
I have customed web page background color