Edit in JSFiddle

#animated_ball {
    width:250px;
    height:250px;
    border-radius:250px;
    background: linear-gradient(red, yellow);
    float: left;
    margin-top: 82px;
    margin-bottom: 0px;
    padding-bottom:0px;
    margin-left: 12px;
    margin-right: 0px;
    opacity:1.0;
    position:absolute;
    cursor:crosshair;
}

#animated_ball:hover{
   animation: spin 0.1s linear infinite;
  -webkit-animation-duration: spin 0.1s linear infinite;
}


@keyframes spin {
  0%   {transform: rotate(0deg);}
    50% {transform: rotate(180deg);}
    100%   {transform: rotate(360deg);}
  }

@-webkit-keyframes spin {
0%   {-webkit-transform: rotate(0deg);}
    50% {-webkit-transform: rotate(180deg);}
    100%   {-webkit-transform: rotate(360deg);}
}