<!DOCTYPE html>
<html>
<head>
<title></title>
<meta charset="utf-8" />
</head>
<body>
<script language="javascript" type="text/javascript">
function overto()
{
seeme.innerHTML=" are you look at me";
}
function moveto()
{
seeme.innerHTML=" ";
}
</script>
<form name="form1" action="#">
<input type="button" name="button1" value="鼠标放上面有提示" onmouseover="javascript:overto()" onmouseout="javascript:moveto()" />
<font id="seeme"> </font>
</form>
</body>
</html>
原文：http://www.cnblogs.com/rysly/p/tooltip.html