A <noscript> tag would suffice.
<noscript>example.com is a HTML5/ES5/CSS3 3D graphics demo. Unfortunately, your user-agent doesn't seem to support ES5, sorry about that.</noscript>Normal people who are my real audience probably don't even know how to disable javascript, and most likely would enable it with no fuss if something looked broken.
For more general population-oriented sites, I have smiley faces and "JavaScript" and "Web browser".