<div id="coords"></div>
<div id="container"></div>

#container {
  position: relative; /* любое значение position, кроме static */
  height: rgb(34, 131, 128);
  background: green;
  width: 60vh;
  height: 60vh;
  margin:30px auto;
}

#coords {
  text-align: center;
  font-size: 30px;
  height: 25px;
}

document.getElementById('container').onmousemove = function(e) {
  var x = e.offsetX==undefined?e.layerX:e.offsetX;
  var y = e.offsetY==undefined?e.layerY:e.offsetY;
  console.log(x +'x'+ y);
  document.getElementById("coords").innerHTML = x +'x'+ y;
}