How compatible is ShaderForge when compiling to HTML5?

As Chrome has recently dropped support for the Unity webplayer, I'm curious how well ShaderForge shaders compile for an HTML5 / WebGL publish. I've heard that there are some shaders that don't work correctly when translated to Javascript, though I wasn't given specifics.

I know that in the past I've had issues with rim shaders functioning on mobile, I'm wondering if I'd have similar problems targetting HTML5.