When querying Service Based Architecture for Dynamics GP, you might get a 'Service is not available' error, it looks like this:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN""http://www.w3.org/TR/html4/strict.dtd">
<HTML>
<HEAD>
<TITLE>Service Unavailable</TITLE>
<META HTTP-EQUIV="Content-Type" Content="text/html; charset=us-ascii">
</HEAD>
<BODY>
<h2>Service Unavailable</h2>
<hr>
<p>HTTP Error 503. The service is unavailable.</p>
</BODY>
</HTML>