The official WebKit implementation on iOS includes WebGL that is not activated by default. The standard Safari browser does not yet support WebGL. However, there are various ways to enable WebGL. We wrote our own instantGLory App and there are some other solutions (e.g. http://demoseen.com/webglenabler/, https://github.com/benvanik/WebGLBrowser), which provide a WebGL browser, and we made sure that X3DOM works smoothly on iOS.
WARNING: There is a bug in x3dom/iOS6 right now so you should stick with iOS5. We have some strange performance issues with iOS6 that seem to be caused by using FBOs. Therefore, you can only use the old “box” mode picking until these issues are resolved.
For a list of supported browsers and possible caveats see the Browser Support page.