<p>I would like my GWT program to be able to determine whether it's in hosted mode or in web mode.  Is there a way to do this?</p>

<p>Thanks! </p>

GWT.isScript() returns true in non hosted mode and false in hosted mode.
http://google-web-toolkit.googlecode.com/svn/javadoc/1.5/com/google/gwt/core/client/GWT.html#isScript()