A WebGL-enabled browser is a requirement of the ArcGIS Maps SDK for JavaScript. This sample shows how to detect if the browser has WebGL enabled, and show a message for browsers that don't.
To test this sample, temporarily turn off WebGL:For example, in Firefox, type "about:config" in URL bar, search for "webgl.disabled" and turn it to true.
To test if your browser has WebGL enabled, you can try get.webgl.org or webglreport.com.