how to write mouseover and mouseout event on image

<%@ Page Language="VB" MasterPageFile="~/M1.master" AutoEventWireup="false" CodeFile="Default.aspx.vb" Inherits="_Default" title="Untitled Page" %>

<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="cc1" %>

<asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">

    <script type="text/javascript" >
    function showIt(imgsrc) {

           var Image_over = new Image();
             var Image_over1=new Image();
            Image_over.src = imgsrc.src;
             Image_over1.src=imgsrc.src;
            var Image1 = document.getElementById("<%=Img1.ClientID%>");
           Image1.src = Image_over.src;
          out()
        }

function out(imgsrc)
{
     var Image_over1=new Image();
     var Image2 = document.getElementById("<%=Img2.ClientID%>");
     Image2.src=Image_over1.src;
}
       function cancelIt(imgsrc)
       {
       var image_out=new Image();

           image_out.src=imgsrc.src;
           image_out1.src=imgsrc.src;
            var image1=document.getElementById("<%=Img1.ClientID %>");

            image1.src=image_out.src;
           ins()
       }
//
function ins(imgsrc)
{
 var image_out=new Image();
 var image2 = document.getElementById("<%=Img2.ClientID%>");
 image2.src=image_out.src;
}
//    if (document.images)   {
//     image1on = new Image();
//     image1on.src="name of your "on" image";

//     image1off = new Image();
//     image1off.src = "name of your "off" image";

//}

//function turnOn(imageName)   {
//     if (document.images)   {
//     document[imageName].src = eval(imageName + "on.src");
//     }
//}

//function turnOff(imageName)   {
//     if (document.images)   {
//     document[imageName].src = eval(imageName + "off.src");
//     }
//}


function IsMobile(sender,e)
{
    e.IsValid = true;
    var Mob=e.Value;

    if(Mob=='END' || Mob=='end')
        {
        e.IsValid=true;
        }
    else
        {
            MyExp=/^([9|8]{1}+\d{9})$/;
            e.IsValid= MyExp.test(Mob)

        }
//
//function bigImg(x)
//{
//x.style.height="200px";
//x.style.width="200px";
//}

//function normalImg(x)
//{
//x.style.height="98px";
//x.style.width="153px";
//}
}


</script>

    <asp:ScriptManager ID="ScriptManager1" runat="server">
    </asp:ScriptManager>
    <p>
    <table style="width: 100%; margin-top: 9px;">
        <tr>
            <td style="width: 286px">
                <asp:Label ID="Label1" runat="server" Font-Bold="True" Text="SL.NO"></asp:Label>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<asp:TextBox
                    ID="txtslno" runat="server" Height="16px" style="margin-left: 0px"
                    Width="123px"></asp:TextBox>
            </td>
            <td style="width: 267px">
&nbsp;
                <asp:Label ID="Label2" runat="server" Font-Bold="True" Text="NAME"></asp:Label>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<asp:TextBox ID="txtname" runat="server"
                    Height="19px" Width="124px"></asp:TextBox>
            </td>
            <td>
                &nbsp;</td>
            <td>
                &nbsp;</td>
        </tr>
        <tr>
            <td style="width: 286px">
                <asp:Label ID="Label3" runat="server" Font-Bold="True" Text="ADDRESS"></asp:Label>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<asp:TextBox
                    ID="txtaddr" runat="server" Height="17px" Width="130px"
                    TextMode="MultiLine"></asp:TextBox>
            </td>
            <td style="width: 267px">
                <asp:Label ID="Label4" runat="server" Font-Bold="True" Text="LANDLINE"></asp:Label>
&nbsp;<asp:TextBox ID="txtlan" runat="server" Height="17px" Width="24px"></asp:TextBox>
                <cc1:FilteredTextBoxExtender ValidChars="0123456789" ID="FilteredTextBoxExtender11"
                                                    runat="server" TargetControlID="txtlan" FilterType="Numbers">
                                                </cc1:FilteredTextBoxExtender>
                                                &nbsp;<asp:TextBox ID="txtlandl" runat="server"
                    Height="18px" Width="127px"></asp:TextBox>
                                                <cc1:FilteredTextBoxExtender ValidChars="0123456789" ID="FilteredTextBoxExtender18"
                                                    runat="server" TargetControlID="txtlandl" FilterType="Numbers">
                                                </cc1:FilteredTextBoxExtender>
                                            </td>
            </td>
            <td>
                <asp:Label ID="Label5" runat="server" Font-Bold="True" Text="MOBILE"></asp:Label>
                &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
                <asp:TextBox ID="txtmbl" runat="server" Height="21px" Width="126px"></asp:TextBox>
                         <asp:RequiredFieldValidator ID="RequiredFieldValidator7" runat="server" ErrorMessage="Enter Mobile No. (Authorized Representative)"
                                                                ControlToValidate="txtmbl" ToolTip="Enter Mobile No">*</asp:RequiredFieldValidator>
                                                            <cc1:FilteredTextBoxExtender ValidChars="0123456789" ID="FilteredTextBoxExtender53"
                                                                runat="server" TargetControlID="txtmbl" FilterType="Numbers">
                                                            </cc1:FilteredTextBoxExtender>
                                                            <asp:CustomValidator runat="server" ID="CustomMobile" ControlToValidate="txtmbl"
                                                                ClientValidationFunction="IsMobile" ErrorMessage="Mobile Number Should Start with 9/8/7"
                                                                ToolTip="Mobile Number Should Start with 9/8/7">*</asp:CustomValidator>
            </td>
            <td>
                &nbsp;</td>
        </tr>
        <tr>
            <td style="width: 286px">
                <asp:Button ID="Button1" runat="server" Font-Bold="True" Text="NEW" />
            </td>
            <td style="width: 267px">
                &nbsp;</td>
            <td>
                &nbsp;</td>
            <td>
                &nbsp;</td>
        </tr>
        <tr>
            <td style="width: 286px">
                &nbsp;</td>
            <td style="width: 267px">
                <asp:Image ID="Img1" runat="server" Height="94px" ImageUrl="~/yellow1.jpg"
                    Width="104px" style="margin-top: 0px" />
            </td>
            <td>
                <asp:Image ID="Img2" runat="server" ImageUrl="~/mobile.bmp" />
            </td>
            <td>
                &nbsp;</td>
        </tr>
        <tr>
            <td style="width: 286px">
                &nbsp;</td>
            <td style="width: 267px">
                &nbsp;</td>
            <td>
                &nbsp;</td>
            <td>
                &nbsp;</td>
        </tr>
    </table>
</p>
</asp:Content>