You can use the View class, like this:
presenter.view.find("#iie_detected").content= View.new('ie_detected.html').to_html
I typically don't like doing things like this from the backend, because it isn't possible to see the result running in prototype mode. In situations like this I usually put the message in the view structure so it's pulled in via view construction, then add a hook to remove it from the view in cases where it isn't needed. Your call though, both are valid options.
Bryan