CSS via Microsoft ISA or TMG

It seems to be very interesting.

As you know, there is one page check out. Without ISA, the page seems to be ok but if a server is behind ISA proxy or fire wall, then CSS render got some issues. ISA server seems to tweak the CSS, which causes this display problem?

The button 'Modify' appeas in the white section just under title bar(.steptitle).
-------------------------------------------------------------------------------------------------------
| Shipping Address                                                                                             |
-------------------------------------------------------------------------------------------------------
                                                                                                                           Modify
....
......
......

When I checked the source, it looks as below.

<div runat="server" id="pnlShippingAddress" class="checkoutstep">
                    <div class="steptitle">
                        <%=GetLocaleResourceString("CheckoutOnePage.ShippingAddress.Title")%>
                        <div style="float: right;">
                            <asp:Button runat="server" ID="btnModifyShippingAddress" Text="<% $NopResources:CheckoutOnePage.ShippingAddress.Modify %>"
                                OnClick="BtnModifyShippingAddress_OnClick" />
                            <ajaxToolkit:CollapsiblePanelExtender runat="server" ID="cpeShippingAddress" TargetControlID="pnlShippingAddressContent" />
                        </div>
                    </div>
                    <asp:Panel runat="server" ID="pnlShippingAddressContent" class="stepcontent">
                        <nopCommerce:CheckoutShippingAddress ID="ctrlCheckoutShippingAddress" runat="server"
                            OnePageCheckout="true" OnCheckoutStepChanged="ctrlCheckoutShippingAddress_CheckoutStepChanged" />
                    </asp:Panel>
                </div>

I did more testing on it and I found that...

I used the same PC with IE. I just changed URL address.
The css renders correctly if I use 'http://localhost/......
if I use http://mypc01/..... then it renders wrong or not what I expect.
Both points at the same location anyway. Any CSS grue can find a problem?

thanks