Java Script Method

Helpfull Java Script Method 

1.   <script language="javascript" type="text/javascript">
        function textboxMultilineMaxNumber(txt, maxLen) {
            try {
                if (txt.value.length > (maxLen - 1)) return false;
            } catch   {
            }
        }
    </script>

 <asp:TextBox ID="txtRemarks" onkeypress="javascript:return textboxMultilineMaxNumber(this,4000)"
  runat="server" TextMode="MultiLine" Width="98%" Height="100"></asp:TextBox>