risolto il problema, ho utilizzato i css invece di ajax:

<STYLE>
A {
COLOR: #000d88;
TEXT-DECORATION: none
}

A:visited {
COLOR: #1b589c;
}

A:hover {
COLOR: #d44700;
BORDER-BOTTOM: #d44700 1px solid;
}

A.info {
POSITION: relative
}
A.info SPAN.tt {
DISPLAY: none
}
A.info:hover SPAN.tt {
DISPLAY: block
}
A.info:hover SPAN.tt {
BORDER-RIGHT: #000 1px solid;
PADDING-RIGHT: 6px;
BORDER-TOP: #000 1px solid;
PADDING-LEFT: 6px;
LEFT: 2em;
PADDING-BOTTOM: 6px;
BORDER-LEFT: #000 1px solid;
WIDTH: 30em;
COLOR: #000;
PADDING-TOP: 6px;
BORDER-BOTTOM: #000 1px solid;
POSITION: absolute;
TOP: 2em;
BACKGROUND-COLOR: #f8f8cb;
TEXT-ALIGN: left
}
</STYLE>

E nel link:

[img]immagine.jpg[/img]<SPAN class=tt>testo tooltip</SPAN>