Problem

When you try to preview an ASPX or PHP page in Expression Web 2, which uses the built-in Microsoft Expression Development Server, you may receive one of the following two errors:

The XML page cannot be displayed

Cannot view XML input using style sheet. Please correct the error and
then click the Refresh button, or try again later.

------------------------------------------------------------------------------------

The server did not understand the request, or the request

was invalid. Error processing resource

'http://www.w3.org/TR/xhtm...

or …..

Page Cannot Be Displayed

Cause

A recent update (signature file 1.53.283.0) for Windows Defender and Microsoft Forefront Client Security released on March 9, 2009 to address a Win32/PossibleHostFileHijack issue. Signature versions 1.53.283.0 and higher include this fix.

If you aren’t sure whether or not you were updated with this signature file, here’s a way to check:

Windows Vista

1. Click the START button > Control Panel
2. In the Control Panel “Classic View” (link on the left side of the page) open Programs and Features
3. On the left column, click the link “View Installed Updates”
4. From the menus near the top of the page, click Views and select Detail. Then right click on the column header labeled “Size” and left click to select “Installed On”. A new column called “Installed On” should appear. Clicking this column header should allow you to sort the items in ascending or descending order. Sort these by the most recent date.
5. Look for Definition update for Windows Defender (KB91557) or Microsoft Forefront Client Security – version 1.53.283.0 or higher

Windows XP

1. Click the START button > Control Panel
2. In the Control Panel “Classic View” (link on the left side of the page) open Add or Remove Programs
3. At the top of the Add or remove Programs dialog, click to select the “Show Updates” checkbox
4. Scroll down to Windows Defender and look beneath that program for the definition update version 1.53.283.0 or higher

How to Resolve

To resolve this problem, do the following:

1. On Windows Vista, click the Start button > All Programs > Accessories and right click on Notepad. Left click on “Run as Administrator”. On Windows XP simply click the Start button > Programs > Accessories and launch Notepad.

2. Click File > Open and navigate to C:\Windows\System32\drivers\etc and open the hosts file

3. In the hosts file below the lines that start with a pound (#) sign, you may have entries, however if you are affected by this issue you will not have an entry for the loopback address for localhost. On a new line add the following:

127.0.0.1       localhost

Use the <TAB> key after the IP address for the correct spacing to add localhost as the hosts file is tab delimited.

4. Click File, Save and close the Hosts file.

This should resolve the issue for not being able to preview ASP.NET and PHP pages in Expression Web 2. This issue also affects ASP.NET Web Development Server as shown here.