SOLVED THANKS TO ELIEL's LINK
What I want to do is to change the body background while hovering on a div, but I can't acquire that, what I get is the div background changed.
I do have the color on the body, which is black, and I want to change it to white if I hover on the div1.
That is what I have tried
body{
background-color:black;
}
#div1:hover {
background-color:white;
}
But this changes my div1 background color instead of the body background color.