Refresh Dropdownlist without postback

I want to refresh the dropdownlist, because on selection of "OTHERS" of the list I want to make visible a textbox.
Pleae suggest me how to implement it. Here is the code:-
<td class="field" style="width: 5%"> <asp:DropDownList ID="ddlTitle" runat="server" Width="100"> <asp:ListItem Selected="True" Value="Select">--Select--</asp:ListItem> <asp:ListItem Value="Mr">Mr</asp:ListItem> <asp:ListItem Value="Miss">Miss</asp:ListItem> <asp:ListItem Value="Mrs">Mrs</asp:ListItem> <asp:ListItem Value="Others">Others</asp:ListItem> ...