If you want to display external HTML content in a layout region then you can add a view like the following
<view id='com.cohga.html.client.view'> <location>center</location> <title>Title</title> <html><![CDATA[ <iframe src="http://server/file.htm" width="100%" height="100%" frameborder="0"/> ]]></html> </view>
This will display the content retrieved from http://server/file.htm in the center layout region.