How to display different asp code on .aspx page, for different browsers, IE, FF or Chrome?

HI,
I'm working on a MVC3 project that contains .aspx code; and currently I'm integrating the new design (html, css, Javascript) with the logic.
I encountered a problem that has to do with display a DDL list (get data from the DB works) - it looks ok in FF, but moved down a bit in IE, also in Chrome. I'm trying to have Different style info written into the <asp:DropDownList>, based on the logic in the codebehind:
The code in the .aspx is:
<asp:DropDownList ID="ddlTicketCategory" runat="server" OnSelectedIndexChanged="ddlTicketCategory_SelectedIndexChanged" class="login_1" DataValueField="TicketCategoryID" DataTextField="TicketCategoryDescription" width="359" Height="31" style='<%# ddlStyle %>' >  </asp:DropDownList>
The logic in the codebehind is:
if (!Page.IsPostBack)
{
         &n ...