Here I will code you how to show the CSS tooltip for the Gridview in asp.net, Here normal tooltip is replaced with the Decorated using JQuery UI and Jquery CSS. Here we need Jquery and Jquery UI plugin and Jquery CSS plugin.

Aspx :

<head runat="server">
<script type="text/javascript" src="http://code.jquery.com/jquery-1.11.3.min.js"></script>
<script type="text/javascript" src="http://code.jquery.com/ui/1.11.4/jquery-ui.js"></script>
<link rel="stylesheet" href="http://code.jquery.com/ui/1.11.4/themes/smoothness/jquery-ui.css" />
    <style type="text/css">
        .ui-tooltip, .arrow:after
            background: #FFFF80;
            border: 1px solid Black;
            padding: 10px 10px;
            color: black;
            border-radius: 10px;
            font: bold 10px "Helvetica Neue" , Sans-Serif;
            text-transform: uppercase;
            box-shadow: 0 0 7px black;
            width: 70px;
            height: 16px;
            overflow: hidden;
            position: absolute;
            left: 50%;
            margin-left: -35px;
            bottom: -16px;
            top: -25px;
            bottom: auto;
            left: 20%;
            content: "";
            position: absolute;
            left: 20px;
            top: -20px;
            width: 25px;
            height: 25px;
            box-shadow: 6px 5px 9px -9px black;
            -webkit-transform: rotate(45deg);
            -ms-transform: rotate(45deg);
            transform: rotate(45deg);
            bottom: -20px;
            top: auto;
    <script type="text/javascript">

        $(function () {
                position: {
                    my: "center bottom-20",
                    at: "center top",
                    using: function (position, feedback) {
    <form id="form1" runat="server">
        <asp:GridView ID="grd_popup_details" HeaderStyle-BackColor="#cccccc" runat="server"
            OnRowDataBound="grd_popup_details_RowDataBound" >

C# :

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.SqlClient;
using System.Data;

namespace TTip
    public partial class ttcss : System.Web.UI.Page
        protected void Page_Load(object sender, EventArgs e)

            SqlConnection con = new SqlConnection("Connection string");
            string Query = "select Query";
            SqlDataAdapter da = new SqlDataAdapter(Query, con);
            DataSet DS = new DataSet();
            grd_popup_details.DataSource = DS;
        protected void grd_popup_details_RowDataBound(object sender, GridViewRowEventArgs e)
            for (int i = 0; i < e.Row.Cells.Count; i++)
                e.Row.Cells[i].ToolTip = e.Row.Cells[i].Text;