jQuery扩展：
jquery.tinywatermark-3.1.0.js文件代码：
(function($) {
$.fn.watermark = function(c, t) {
var e = function(e) {
var i = $(this);
if (!i.val()) {
var w = t || i.attr('title'), $c = $($("<div />").append(i.clone()).html().replace(/type=\"?password\"?/, 'type="text"')).val(w).addClass(c);
i.replaceWith($c);
$c.focus(function() {
$c.replaceWith(i); setTimeout(function() {i.focus();}, 1);
})
.change(function(e) {
i.val($c.val()); $c.val(w); i.val() && $c.replaceWith(i);
})
.closest('form').submit(function() {
$c.replaceWith(i);
});
}
};
return $(this).live('blur change', e).change();
};
})(jQuery);
或者访问网址：http://plugins.jquery.com/files/jquery.tinywatermark-3.1.0.js_.txt
用法：
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>WaterMark</title>
<script src="../JS/jquery-1.5.2.min.js" type="text/javascript"></script>
<script src="../JS/jquery.tinywatermark-3.1.0.js"type="text/javascript"></script>
<script type="text/javascript" language="javascript">
$(function()
{
$("input[title='Month']").watermark('watermark','Title');
$("textarea[title='Content']").watermark('watermark','Please input the content !');;
});
</script>
<style type="text/css">
.watermark {color:#999;}
</style>
</head>
<body>
<form id="form1" runat="server">
<div>
<div><input title="Month"/></div>
<div><textarea id="TextArea1" cols="20" rows="2" title="Content"></textarea></div>
</div>
</form>
</body>
</html>