HTML-Tooltip position relative to mouse pointer

How to align the tooltip the natural style: right bottom of the mouse pointer?

<!DOCTYPE html>
<html>
<head>
  <title>Tooltip with Image</title>
  <meta charset="UTF-8">
  <style type="text/css">
    .tooltip {
        text-decoration:none;
        position:relative;
    }
     .tooltip span {
        display:none;
    }
     .tooltip span img {
        float:left;
    }
     .tooltip:hover span {
        display:block;
        position:absolute;
        overflow:hidden;
    }
  </style>
</head>
<body>
  <a class="tooltip" href="http://www.google.com/">
    Google
    <span>
      <img alt="" src="http://www.google.com/images/srpr/logo4w.png">
    </span>
  </a>
</body>
</html>

Solution

For default tooltip behavior simply add the title attribute. This can't contain images though.

<div title="regular tooltip">Hover me</div>

Before you clarified the question I did this up in pure JavaScript, hope you find it useful. The image will pop up and follow the mouse.

jsFiddle

JavaScript

var tooltipSpan = document.getElementById('tooltip-span');

window.onmousemove = function (e) {
    var x = e.clientX,
        y = e.clientY;
    tooltipSpan.style.top = (y + 20) + 'px';
    tooltipSpan.style.left = (x + 20) + 'px';
};

CSS

.tooltip span {
    display:none;
}
.tooltip:hover span {
    display:block;
    position:fixed;
    overflow:hidden;
}

Extending for multiple elements

One solution for multiple elements is to update all tooltip span's and setting them under the cursor on mouse move.

jsFiddle

var tooltips = document.querySelectorAll('.tooltip span');

window.onmousemove = function (e) {
    var x = (e.clientX + 20) + 'px',
        y = (e.clientY + 20) + 'px';
    for (var i = 0; i < tooltips.length; i++) {
        tooltips[i].style.top = y;
        tooltips[i].style.left = x;
    }
};