You will find a "Code" button on our message editor that can wrap special tags around Java code, XML, and other pre-formatted text. It makes them easier to read.
If you get a blank page when using a template or include, there's a problem with the template that is being included.
Unfortunately, there's not likely to be any helpful messages, so what I do is strip down the included file to something basic like a "hello" outputText and keep adding back what I took out until I find the failing element.
An IDE is no substitute for an Intelligent Developer.