I've investigated the page, but please simplify the code as much as you can leaving only required to reproduce the problem and related to that problem.
For example, you could totally remove "meta:resourcekey" things.
I think it's not possible to get a cross-browser RTL solution only via CSS, needs to use a respective layout.
Please look at the example.
Example
<%@ Page Language="C#" %>
<%@ Register Assembly="Ext.Net" Namespace="Ext.Net" TagPrefix="ext" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title>Ext.NET Example</title>
<style type="text/css">
.rtl {
direction: rtl;
}
</style>
</head>
<body>
<form runat="server">
<ext:ResourceManager runat="server" />
<ext:FormPanel
runat="server"
Title="Login"
ButtonAlign="Left"
Height="200"
Width="400"
Padding="5"
Icon="Lock"
DefaultAnchor="100%">
<Items>
<ext:CompositeField runat="server">
<LayoutConfig Pack="End" />
<Defaults>
<ext:Parameter Name="cls" Value="rtl" Mode="Value" />
</Defaults>
<Items>
<ext:ComboBox runat="server" Width="150" />
<ext:DisplayField runat="server" Text="ComboBox:" Width="100" />
</Items>
</ext:CompositeField>
<ext:CompositeField runat="server">
<LayoutConfig Pack="End" />
<Defaults>
<ext:Parameter Name="cls" Value="rtl" Mode="Value" />
</Defaults>
<Items>
<ext:TextField runat="server" Width="150" />
<ext:DisplayField runat="server" Text="User name:" Width="100" />
</Items>
</ext:CompositeField>
<ext:CompositeField runat="server">
<LayoutConfig Pack="End" />
<Defaults>
<ext:Parameter Name="cls" Value="rtl" Mode="Value" />
</Defaults>
<Items>
<ext:TextField runat="server" Width="150" />
<ext:DisplayField runat="server" Text="Password:" Width="100" />
</Items>
</ext:CompositeField>
<ext:CompositeField runat="server">
<LayoutConfig Pack="End" />
<Defaults>
<ext:Parameter Name="cls" Value="rtl" Mode="Value" />
</Defaults>
<Items>
<ext:Checkbox runat="server" Width="15" />
<ext:DisplayField runat="server" Text="Checkbox:" Width="100" />
</Items>
</ext:CompositeField>
</Items>
<Buttons>
<ext:Button runat="server" Icon="Lock" Text="Login" />
</Buttons>
</ext:FormPanel>
</form>
</body>
</html>
Unfortunately, I think it's impossible to get your initial sample to be working the same way under all browsers.
We can try to help with some concrete RTL issue, but, unfortunately, we can't provide you with a full RTL solution since it's a really big deal.
We hope that it will be implemented in ExtJS 4 and, respectively, in Ext.NET v2.