//Page
<span class="ToolTip">Info text goes here…</span>
<span class="ToolTip">Another info text goes here…</span>

//CSS
.ToolTip {cursor:help; width:16px; height:16px;display:block;background:url(images/help.png);font-size:0%;line-height:1px;overflow:hidden;}

//JS
window.onload = function () {
var myArray = getElementsByClassName(document, "span", "ToolTip");
for ( var i=0, len=myArray.length; i<len; ++i ){
myArray[i].onmouseover = function () {
tooltip.show(this.innerHTML);
};
myArray[i].onmouseout = function () {
tooltip.hide();
};
}
};

function getElementsByClassName(oElm, strTagName, strClassName){
var arrElements = (strTagName == "*" && oElm.all)? oElm.all : oElm.getElementsByTagName(strTagName);
var arrReturnElements = new Array();
strClassName = strClassName.replace(/\-/g, "\\-");
var oRegExp = new RegExp("(^|\\s)" + strClassName + "(\\s|$)");
var oElement;
for(var i=0; i<arrElements.length; i++){
oElement = arrElements[i];
if(oRegExp.test(oElement.className)){
arrReturnElements.push(oElement);
}
}
return (arrReturnElements)
};