var dw_event = {
  add: function(obj, etype, fp, cap) {
    cap = cap || false;
    if (obj.addEventListener) obj.addEventListener(etype, fp, cap);
    else if (obj.attachEvent) obj.attachEvent("on" + etype, fp);
  },
  remove: function(obj, etype, fp, cap) {
    cap = cap || false;
    if (obj.removeEventListener) obj.removeEventListener(etype, fp, cap);
    else if (obj.detachEvent) obj.detachEvent("on" + etype, fp);
  },
  DOMit: function(e) {
    e = e? e: window.event;
    e.tgt = e.srcElement? e.srcElement: e.target;
    if (!e.preventDefault) e.preventDefault = function () { return false; }
    if (!e.stopPropagation) e.stopPropagation = function () { if (window.event) window.event.cancelBubble = true; }
    return e;
  }
 
}

var Tooltip = {
  followMouse: true,
  offX: 8,
  offY: 12,
 
  ready: false,
  t1: null,
  t2: null,
  tipID: "tipDiv",
  tip: null,
 
  init: function() {
    if ( document.createElement && document.body && typeof document.body.appendChild != "undefined" ) {
      var el = document.createElement("DIV");
      el.className = "tooltip";
      el.id = this.tipID;
      document.body.appendChild(el);
      this.ready = true;
    }
  },
 
  show: function(e, msg) {
    if (this.t1) clearTimeout(this.t1);   
     if (this.t2) clearTimeout(this.t2);
    this.tip = document.getElementById( this.tipID );
     // set up mousemove
     if (this.followMouse)
      dw_event.add( document, "mousemove", this.trackMouse, true );
    this.writeTip("");  // for mac ie
    this.writeTip(msg);
    viewport.getAll();
    this.positionTip(e);
     this.t1 = setTimeout("document.getElementById('" + Tooltip.tipID + "').style.visibility = 'visible'",200);   
    },
   
    writeTip: function(msg) {
      if ( this.tip && typeof this.tip.innerHTML != "undefined" ) this.tip.innerHTML = msg;
    },
   
    positionTip: function(e) {
      var x = e.pageX? e.pageX: e.clientX + viewport.scrollX;
      var y = e.pageY? e.pageY: e.clientY + viewport.scrollY;

      if ( x + this.tip.offsetWidth + this.offX > viewport.width + viewport.scrollX )
        x = x - this.tip.offsetWidth - this.offX;
      else x = x + this.offX;
   
      if ( y + this.tip.offsetHeight + this.offY > viewport.height + viewport.scrollY )
        y = ( y - this.tip.offsetHeight - this.offY > viewport.scrollY )? y - this.tip.offsetHeight - this.offY : viewport.height + viewport.scrollY - this.tip.offsetHeight;
      else y = y + this.offY;
 
      this.tip.style.left = x + "px"; this.tip.style.top = y + "px";
    },
   
    hide: function() {
      if (this.t1) clearTimeout(this.t1);   
       if (this.t2) clearTimeout(this.t2);
      this.t2 = setTimeout("document.getElementById('" + this.tipID + "').style.visibility = 'hidden'",200);
       // release mousemove
       if (this.followMouse)
          dw_event.remove( document, "mousemove", this.trackMouse, true );
      this.tip = null;
    },
   
    trackMouse: function(e) {
       e = dw_event.DOMit(e);
       Tooltip.positionTip(e);   
    }

}

Tooltip.init();

var viewport = {
  getWinWidth: function () {
    this.width = 0;
    if (window.innerWidth) this.width = window.innerWidth - 18;
    else if (document.documentElement && document.documentElement.clientWidth)
        this.width = document.documentElement.clientWidth;
    else if (document.body && document.body.clientWidth)
        this.width = document.body.clientWidth;
  },
 
  getWinHeight: function () {
    this.height = 0;
    if (window.innerHeight) this.height = window.innerHeight - 18;
     else if (document.documentElement && document.documentElement.clientHeight)
        this.height = document.documentElement.clientHeight;
     else if (document.body && document.body.clientHeight)
        this.height = document.body.clientHeight;
  },
 
  getScrollX: function () {
    this.scrollX = 0;
     if (typeof window.pageXOffset == "number") this.scrollX = window.pageXOffset;
     else if (document.documentElement && document.documentElement.scrollLeft)
        this.scrollX = document.documentElement.scrollLeft;
     else if (document.body && document.body.scrollLeft)
        this.scrollX = document.body.scrollLeft;
     else if (window.scrollX) this.scrollX = window.scrollX;
  },
 
  getScrollY: function () {
    this.scrollY = 0;   
    if (typeof window.pageYOffset == "number") this.scrollY = window.pageYOffset;
    else if (document.documentElement && document.documentElement.scrollTop)
        this.scrollY = document.documentElement.scrollTop;
     else if (document.body && document.body.scrollTop)
        this.scrollY = document.body.scrollTop;
     else if (window.scrollY) this.scrollY = window.scrollY;
  },
 
  getAll: function () {
    this.getWinWidth(); this.getWinHeight();
    this.getScrollX();  this.getScrollY();
  }
 
}

div#tipDiv {
  position:absolute; visibility:hidden; left:10; top:0; z-index:10000;
  /* Ici vous choisissez la couleur et l'image de fond de l'info bulle */
  background:#000000 url(image.gif');
  border:0px solid #FFFFFF;
  /* Ici vous choisissez la largeur de l'info bulle */
  width:250px;
  padding:0px;
  /* Ici vous choisissez la couleur du texte */
  color:#FFFFFF;
  font-size:12px
}
div.tp1 { font-size:12px; color:#FFFFFF; padding-top:5px }

<script src="tooltip/dw_event.js" type="text/javascript"></script>
<script src="tooltip/dw_viewport.js" type="text/javascript"></script>
<script src="tooltip/dw_tooltip.js" type="text/javascript"></script>
<script type="text/javascript">
function doTooltip(e, msg) {
   if ( typeof Tooltip == "undefined" || !Tooltip.ready ) return;
   Tooltip.show(e, msg);
}

function hideTip() {
   if ( typeof Tooltip == "undefined" || !Tooltip.ready ) return;
   Tooltip.hide();
}
</script>

<script type="text/javascript">
var tool_test='<b>Coucou</b><br>Ceci est l'info.';
</script>

<img src="image.gif" onMouseOver="doTooltip(event,tool_test)" onMouseOut="hideTip()">