How to make a user to enter only numeric values in a textbox using Javascript ?

Suppose, you have a textbox where you want a user can enter only numerical values, then write the following script method inside the head section of your page.
 <script type="text/javascript">   

        function isNumberKey(evt) {

            var charCode = (evt.which) ? evt.which : event.keyCode;

            if (charCode > 31 && (charCode < 48 || charCode > 57))

                return false;

            return true;

        }       

    </script>

Then,call this method in the "onkeypress" event of your textbox.

<asp:TextBox ID="txtPhoneNo" runat="server" onkeypress="return isNumberKey(event)">

    </asp:TextBox>

Now, as a result the user can not enter any non-numeric value into that textbox.

Regards,

Prajanuranjan....