Stereo 3D TVs recognizing side by side stereo web content?

I’d like to report on another interesting case that has happened several times in the lab while testing 3D stimuli.

To set the context, we (Alexey and myself) have created a set of tools that create side by side stimuli for the web.These tools use HTML5 canvas and jQuery+HTML5. It generally happens that when we connect via HDMI the PC to the TV (in our case, Active 46”) if the content is side by side (HTML, Canvas, etc) the TV automatically changes to 3D mode.

We find this  interesting since there is no indication from the webpage that tells the TV it is displaying “stereoscopic content”.