var addEvent;

if (document.addEventListener)
{
    addEvent = function(element, type, handler)
    {
        element.addEventListener(type, handler, null);
    }
}
else if (document.attachEvent)
{
    addEvent = function(element, type, handler)
    {
        element.attachEvent("on" + type, handler);
    }
}
else
{
    addEvent = new Function; // not supported
}