Looks like Opengl ES Shading Language is completely missed from the intel driver. Thus firefox nightly is unable to execute any webpages containing webGL contents.
It fails with:
Can't find symbol 'ActiveTexture'
Im interested when it is planned supporting OpenGL shading language version 1.2 (which supports GLSL ES) in intel drivers?

Here is a more detailed thread at khronos' forum:

Best regards,