This is sample example for Add,Remove Class in Textbox on focus and on Blur using JQuery and ASP.NET.
Sample Code
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title>Changing Textbox class on focus in JQuery</title>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js">
</script>
<script type="text/javascript">
$(document).ready(function()
{
$('INPUT[type="text"]').focus(function() {
$(this).addClass("focus");
});
$('INPUT[type="text"]').blur(function() {
$(this).removeClass("focus");
});
});
</script>
<style type="text/css">
.focus {
border: 2px solid red;
background-color: #FEFED5;
}
</style>
</head>
<body>
<form id="form1"
runat="server">
<div>
<table>
<tr>
<td><b>FirstName:</b></td>
<td><asp:TextBox ID="txtFName"
runat="server"/></td>
</tr>
<tr>
<td><b>LastName:</b></td>
<td><asp:TextBox ID="txtLName"
runat="server"/></td>
</tr>
<tr>
<td><b>City:</b></td>
<td><asp:TextBox ID="txtCity"
runat="server"/></td>
</tr>
<tr>
<td></td>
<td><asp:Button ID="btnSubmit"
runat="server"
Text="Submit"/></td>
</tr>
</table>
</div>
</form>
</body>
</html>