Code from http://jsfiddle.net/vWYQ2/2/, this removes the hyperlink once mouse is out.
HTML
<div id="TA" onmousemove="changetext();" onmouseout="restore();">I am a JavaScript hacker.</div>
JavaScript
var originalBlock = document.getElementById("TA").innerHTML;
var timer;
function changetext()
{
var id = document.getElementById("TA");
if(originalBlock == null) originalBlock= id.innerHTML;
var text = id.innerHTML;
id.innerHTML = text.replace("JavaScript hacker", "<a href='foo.php'>JavaScript hacker</a>");
if(timer != null)
clearTimeout(timer);
}
function restore()
{
timer = setTimeout(function()
{
document.getElementById("TA").innerHTML = originalBlock;
}, 1000);
}