I found it useful also. I adapted it for my own needs however!
Changed slightly:

<span onmouseover=\'JavaScript:a(\"Hawkee\")\' onmouseout=\'Javascript:a(\"Null\")\' >Hawkee.com
and added this to the end of the Javascript cases(before two final \'} }\' ):
case \"Null\":
document.getElementById(\"data\").innerHTML = \"\";
break;
This means that when the mouse no longer hovers over, the text vanishes!