ASP.NET - javascript confirm message box using 'Yes' 'No' text

function confirm_proceed()
        {
            if (confirm("Are you sure you want to proceed?")==true)
                return "YES";
            else
                return "NO";
        }

The web is rapidly changing, and you would need to look beyond the normal Confirm dialogs. 

The Ajax Control toolkit of ASP.Net provides the Modal Popup Extender control that gives you exactly what you need. You can find the entire description and its properties http://www.asp.net/ajax/ajaxcontroltoolkit/samples/modalpopup/modalpopup.aspx.

In its simplest form, it would look like:
<ajaxToolkit:ModalPopupExtender runat="server" ID="myMPE" 
    PopupControlID="myPanelWithButtons"    OkControlID="OkayButtonID" 
    OnOkScript="ScriptToExecute"   CancelControlID="CancelButtonID" 
/>

And the Panel "myPanelWithButtons" would need to have a markup like:
<asp:Panel ID="myPanelWithButtons" runat="server" >
<br />What is your option?<br />
<asp:Button ID="OkayButtonID"    runat="server" Text="OK" />
<asp:Button ID="CancelButtonID" runat="server" Text="Cancel" />
</asp:Panel>

Additionally, you can use CSS and beautify this control to your heart's content. An interesting point that has to be mentioned is the ability that the Modal Popup extender to behave as a Modal dialog which is what we ideally need when receiving mandatory user input.
 

If you want to show popup then use jquery popup.

after adding jqueryui plugin you can use it.

like this-

<script>

function funShow() {

$('#dialog).dialog({ resizable: false, height: 140, modal: true });

}
</script>

<div id="dialog" title="Basic dialog">hi
</div>

<asp:Button runat="server" Text="Button" onClientClick="return funShow()" />

FOR EXAMPLE FOLLOW THIS

-http://jqueryui.com/demos/dialog/

You can do it by the following code.

Write the following code in your HTML Page.

The buttons in a confirmation box cannot be changed by Javascript.

I would suggest rolling your own in the form of an inline popup. Just create a div with position:absolute; in the centre of the page and then show/hide it.

The code below will outline what you need to do in vanilla Javascript. You will probably want to spend more time styling it, but the key points are:

position:absolute; So that the popup will appear in the centre of the page.display:none; So that the popup will be hidden when the page loads. The link has a href so that it will still be functional even without Javascript. The onClick attribute of the first link has return false; This stops the link from redirecting.

You can change the two onClicks inside the popup to do whatever else you want them to.

<style type="text/css"> 
div#popup 
{ 
    position:absolute; 
    display:none; 
    top:200px; 
    left:50%; 
    width:500px;  
    margin-left:-250px; 
    border:1px solid blue;  
    padding:20px; 
    background-color:white; 
} 
</style> 
<a  
    href="http://example.com/"  
    onClick="document.getElementById('popup').style.display = 'block'; return false;" 
>Go to example.com</a> 
<div id="popup"> 
    <p>Are you sure you want to go to example.com?</p> 
    <p> 
        <a onclick="document.location='http://example.com/'; return false;"> 
            Yes 
        </a> 
        <a onclick="document.getElementById('popup').style.display = 'none'; return false;"> 
            No 
        </a> 
    </p> 
</div> 

<cc1:ScriptManager ID="ScriptManager1" runat="server"/>  
<cc1:ModalPopupExtender TargetControlID="Button2" BackgroundCssClass="modalBackground"
  CancelControlID="btnMsg" PopupControlID="panEdit" PopupDragHandleControlID="btnMsg"
  ID="ModalPopupExtender1" runat="server">
</cc1:ModalPopupExtender>
<cc1:UpdatePanel ID="up1" runat="server" UpdateMode="Conditional">
  <ContentTemplate>
    <asp:Panel ID="panEdit" runat="server" CssClass="ModalWindow">
      <%--Button popup--%>
      <center>
        <asp:Label ID="Label1" runat="server" Text="Are you Sure you want to Exit?"/>
        <asp:TextBox Visible="false" ID="TextBox1" runat="server"></asp:TextBox><br />
        <asp:Button ID="btnMsg" runat="server" BorderWidth="0" Text="OK" /><br />
        <asp:Button ID="btn2" runat="server" BorderWidth="0" Text="Cancel" /><br />
        <br />
      </center>
    </asp:Panel>
  </ContentTemplate>
</cc1:UpdatePanel>

<style type="text/css">
  .modalBackground
  {
    background-color: #CCCCFF;
    filter: alpha(opacity=40);
    opacity: 0.5;
  }
  .ModalWindow
  {
    border: solid1px#c0c0c0;
    background-color: #99ccff;
    padding: 0px10px10px10px;
    position: absolute;
    top: -1000px;
  }
</style>