Problem : this is not working!!
HTML
<div id="circle1" class="circle"></div>
<div id="circle2" class="circle"></div>
<div id="circle3" class="circle"></div>
JS
var circle = document.getElementsByClassName('circle');
circle.onmouseover = function(){ /* This is not working */
document.write("Hovering over one of the element that contains circle class");
}