Javascript with asp.net confusion

Hi all,
Im trying to use asp.net web controls with javascript and i feel like im getting abit confused here. To start off with when I create a dropdown list using asp as such:
<asp:DropDownList ID="car1_q1" runat="server" style="width: 170px;"  onchange="revealTester(this)">
              <asp:ListItem Value="Not selected">Please select</asp:ListItem>
              <asp:ListItem>None</asp:ListItem>
              <asp:ListItem>Yes</asp:ListItem>
              <asp:ListItem>No</asp:ListItem>
</asp:DropDownList>
This code works perfectly fine, however i have used the style=&q ...