ASP.NET

<img src=""  id="test" alt="test" class="thumbnailImage" onmousemove="zoomImage('test')" onmouseout="hideImage('test')"  runat="server"/>
<asp:FileUpload ID="FileUpload1" runat="server" Style="z-index: 100; left: 337px;
            position: absolute; top: 384px" Height="32px" Width="1px" Font-Size="Small" />

<cc1:TabContainer ID="infotab" runat="server" ActiveTabIndex="1" >
           <cc1:TabPanel ID="TabBranchpanel" runat="server">
           <HeaderTemplate>Orders</HeaderTemplate>
           <ContentTemplate>

<asp:UpdatePanel ID="pannelupdate" runat="server"  UpdateMode="Conditional"   ChildrenAsTriggers="true"><ContentTemplate><asp:DropDownList ID="ddlconnectivity" runat="server" AutoPostBack="true" OnSelectedIndexChanged="ddlconnectivity_SelectedIndexChanged"><asp:ListItem Value="DSL">DSL</asp:ListItem><asp:ListItem Value="Connect">Connect</asp:ListItem><asp:ListItem Value="Not Available">Not Available</asp:ListItem><asp:ListItem Value="Others">Others</asp:ListItem></asp:DropDownList></ContentTemplate><Triggers> 
<asp:AsyncPostBackTrigger ControlID="ddlconnectivity" EventName="SelectedIndexChanged"/>
</Triggers></asp:UpdatePanel>


protected void ddlconnectivity_SelectedIndexChanged(object sender, EventArgs e)
    {
        if (ddlconnectivity.SelectedValue =="Dsl"||ddlconnectivity.SelectedValue=="Connect" || ddlconnectivity.SelectedValue == "Others")
        {

            txtconnectaccount.Visible=true;

        }
        else {
            txtconnectaccount.Visible = false;
        }
    }