jquery in asp.net pages.you may use
if in php pages too.it's nice and appealing -
<head runat="server">
<title>Untitled Page</title>
<script type="text/javascript" 
src="Script/jquery-1.4.2.js"></script>
<script type="text/javascript">
$(document).ready(function(){
 $("#input").focus(function(){
 $("#input").animate({width:"200px"});
 });
 $("#input").blur(function(){
 $("#input").css("width","50px");
 });
 
 });
</script>
<style type="text/css"> 
.textstyle
{
 width:50px;
}
</style>
</head>
<body>
<form id="form1" runat="server"> 
<asp:ScriptManager ID="s1" runat="server">
</asp:ScriptManager> 
<asp:UpdatePanel ID="u1" runat="server">
<ContentTemplate>
<div id="test" style="margin-top:20px;">
Enter your name: <br /> 
<%--<input type="text" id="input" 
style="width:50px;" />--%>
<asp:TextBox ID="input" CssClass="textstyle" 
runat="server" /></div>
</ContentTemplate>
</asp:UpdatePanel></form></body></html>
happy jquery programming