How consistent is video viewing on websites?

[cckgz4]

For example, say I own a Windows Phone device and I go to Engadget's website and look at a video review. On my iPhone, I'm able to view the video. Is it supported for Windows Phone? I think the format is MP4

 

[DBDev]

Almost every video I have tried seems to work. I tried Engadget now and it worked on my Lumia 800 and it is probably the same on WP8