Autofit textboxes and dropdown lists

When I put an ASP.NET 2.0 gridview or formview control into edit mode and display a text box or dropdownlist, I want to be able to react to the browser's font size and to my liquid layout. The best I've been able to come up with is by using skinids as follows:
<asp:textbox runat="server" skinid="AutoFitTextBox"
             width="88%"
             font-size="100%"
             backcolor="#ffff99"
             bordercoler="#4169e1"
             borderwidth="1px"
             borderstyle="solid"/>
<asp:dropdownlist runat="server" skinid="AutoFitDropDownList"
                  width="90%"
                  font-size="100%"
                  backcolor="#ffff99"/>

Then in my edititemtemplate I use something like:
<asp:TextBox ID="txtDrivewayGateSpecify" runat="server"
                                     Text='<%#Bind("DrivewayGateSpecify") %>'
                                     SkinID="AutoFitTextBox"/>

<asp:DropDownList ID="ddlFenceBreezeTypeName" runat="Server"
                             DataValueField="FenceTypeID"
                             DataTextField="Name"
                             DataSourceID="odsFenceTypeName"
                             SelectedValue='<%#Bind("FenceBreezeTypeID") %>'
                             SkinID="AutoFitDropDownList"
                             AppendDataBoundItems="true">
                            <asp:ListItem />
                            </asp:DropDownList>
Although this works reasonalby well (it adjusts both the height and width), it's nowhere near what I would like. Does anyone have a better way?