how to generate alert & confirm box in ASP .Net

<script language="javascript" type="text/javascript">
function ValidateForm()
    {    
          var Form=document.getElementById('frmname');
          if(Form.txtCandidateName.value=='')
          {
              alert('Enter Name of Applicant ');
              document.getElementById('txtCandidateName').focus();
              return false;
          }
          
return true;

function ConfirmALL(btn)
     {
    
      var gr1;
      
      gr1= true;
      
      if(document.getElementById("fldGraduation"))
      {
        gr1= false;
        gr1= validationF();
      }
      
      if(!gr1)
      {
        return false;
      }
      
    
      if(confirm('Yes, I have Checked all the details.')){btn.style.display='none'; return true;}else{return false;}

     }
</script>

<asp:Button ID="btnProceed" runat="server" Text="Proceed" OnClick="btnProceed_Click"                                                    OnClientClick="return ConfirmALL(this);" />

<script type="text/javascript">
       function confirmation() {
            var txtValue=document.getElementById("txtValue");
             if(<pre lang="cs">txtValue<pre lang="cs">.value=="")
             {
                alert("Enter Some Data");
                return false;
              }
             else
              {
                  return  confirm("are u sure?");
              }

       }
   </script >
calling of Function
<asp:button id="btnClick" runat="server" text="Click" xmlns:asp="#unknown">
        OnClientClick="return confirmation();" onclick="btnClick_Click"/></asp:button>

Hope it will help u 
best Luck

<script type="text/javascript">
       function confirmation() {
           if (confirm('are you sure you want to delete ?')) {
           return true;
           }else{
           return false;
           }
       }
   </script>

<asp:button id="Button1" runat="server" text="Button" xmlns:asp="#unknown">
        OnClientClick="return confirmation();" onclick="Button1_Click"/></asp:button>

<asp:textbox id="TextBox1" runat="server" xmlns:asp="#unknown"></asp:textbox>
        <input type="button" value="Show" onclick="checkValidation();" />

function checkValidation()
        {
            var textValue = $('input[id$=TextBox1]').val();

            if (textValue != "")
            {
                if (confirm('Are you sure you want to redirect Page?'))
                {
                    window.location = 'About.aspx';//link to redirect page
                }
                else
                {
                    $('input[id$=TextBox1]').focus(); 
                    return false;
                }
            }
            else
            {
                alert('TextBox is Empty');
             }

        }

String csScriptText = "if (confirm('Are you sure you want to leave the page')){document.location='Default.aspx';}";

Response.Write("<script>alert('"+ Server.HtmlEncode(ex.Message) +"')</script>");