Place DIV on top of page when page is scrolling using CSS

Hi,

i call JS function to display a confirmation message and place it at the top of the window for 5 seconds as follows:

C#:

ScriptManager.RegisterStartupScript(UpdatePanel3, UpdatePanel3.GetType(), "ShowCurrentTime", "ShowCurrentTime();", true);

JS:

        var i = 0;
        function ShowCurrentTime() {
            document.getElementById("Message").style.display = 'block';
            var dt = new Date();
            i++;
            if (i == 5) {
                i = 0;
                document.getElementById("Message").style.display = 'none';
                return false;
            }
            window.setTimeout("ShowCurrentTime()", 1000); // Here 1000(milliseconds) means 1 sec
            return false;
        }

CSS:

.messageboxGreen
{
    background-color: #FFFFFF;
    color: #28b007;
    font-size: large;
    width:200px;
    height:61px;
    margin:0 auto;
    display:none;
    text-align:center;
    border-color:grey;
    border-style:solid;
    border-width:1px;
}

 ASPX:

            <div>
                <div id="Message" class="messageboxGreen">
                        <div style="padding-top:5px;">
                            <asp:Label ID="lblMessage" runat="server" style=" font-weight:bold; font-size:large;"></asp:Label>
                        </div>
                        <div style="padding-top:11px;">
                            <asp:Image ID="imgPNGLogo" runat="server" Width="30px" ImageUrl="~/images/V.png"/>
                        </div>
                </div>
            </div>

Now, somtimes the calling executing when the user scroll down the page so he can't see the popup message.

My question is how can i display the popup message at the top, BUT accordingly to the scroller that the user will be able to see it?

Thanks