Style those divs problem, browser settings fine


getting this error message: "Oops, try again.
Make sure your

s are 100 pixels high! (If your height
looks correct, make sure your border-radius is 100%, not 100px!)"

I have checked my browser's zoom multiple times, changed it and then reset it to default, still won't work. Using firefox.
Any idea what's going wrong?

this is my code:

div {
    display: inline-block;
    margin-left: 5px;
    height: 100px;
    width: 100px;
    border: 2px solid black;
    border-radius: 100%;


Fixed the problem by using Google Chrome instead, still not sure why it wasn't working.