学步园

     <script type="text/javascript">
        function IsNum()
        {  
            var r = document.getElementById("tb1").value;
            alert(r);
            alert(parseFloat(r));
            if( isNaN(parseFloat(r)) || parseFloat(r)<0 || parseFloat(r) != r )
            {
                alert("您必须输入一个大于等于0的数字");
                document.getElementById("tb1").focus();
                return false;
            }
           
         return true;  
        }
    </script>

<asp:TextBox ID="tb1" runat="server" onblur="IsNum()"></asp:TextBox>