Well that's two questions in one post, is that legal?????(jejejeje just
kidding)
Web matrix is an excellent free IDE and I also use it for experimental
projects.
The first thing you need it’s an emulator, the best one is Openwave Phone
Simulator 6.2.2, you can download it from here
http://developer.openwave.com/dvl/tools_and_sdk/openwave_mobile_sdk/phone_simulator/

With that installed all you have to do its run your project on webmatrix so
it starts the web server (code name Cassini) and put it to run in one port
(i.e 8080). Then close IE and launch the Openwave PS and type the address of
the project (it should start like http://localhost:8080/....), and voila!!!
You are previewing your mobile web site in one of the most popular browser
for mobile phones in the world!!! (Compatibility guaranteed with most
devices!!!).

If what you want is to upload it to your server you must start remove the
first line of code web matrix creates that looks like this:
<%@ Page Inherits="Microsoft.Matrix.Framework.Mobile.UI.MobilePage,
Microsoft.Matrix.Framework.Mobile, Version=0.6.0.0, Culture=neutral,
PublicKeyToken=6f763c9966660626" Language="C#" %>
<%@ Register TagPrefix="Mobile" Namespace="System.Web.UI.MobileControls"
Assembly="System.Web.Mobile" %>

and replace irt with this one:

<%@ Page Inherits="System.Web.UI.MobileControls.MobilePage" Language="c#" %>
<%@ Register TagPrefix="mobile" Namespace="System.Web.UI.MobileControls"
Assembly="System.Web.Mobile" %>
<%@ import Namespace="System.Web.Mobile" %>
<script runat="server">

the problem (as you can see) is that web matrix is calling the assembly
Microsoft.Matrix.Framework.Mobile.UI.MobilePage, that it’s not going to be
available in your instaspace server and that’s why you get the error, not
because they can’t run mobile pages.

I hope my post it’s helpful and if you have trouble please let me know

--

Juan David Gomez A.
Microsoft Certified Professional
Analista de Desarrollo - PSL S.A.
Web and Wireless Banking
Medellin - Colombia