Show/Hide div, with plain JS

Question

My CSS:

#a_x200{
    visibility: hidden;
    width: 200px;
    height: 200px;
    background-color: black;
}

My JS:

Answer 1

You're using visibility: hidden to hide it, then attempting to use the display CSS property to make it visible. They're two completely separate properties, changing one won't magically change the other.

If you want to make it visible again, change the value of the visibility property to visible:

document.getElementById('a_x200').style.visibility = 'visible';