HTML5 might helps slowness of Udacity's videos.

Recently I resumed studying programming on Udacity, starting with algorithm course.

However, the videos very often get slow and lag - I could't even recognize what was the sentence teachers said. Then I got to check what is wrong with that.

Chrome's task manager showed adobe flash player consumed many CPU capacity. I suspected that flash player, known for Steve Jobs hated it, is doing something bad while loading a youtube videos incorporated in Udacity.

And I ended up with finding HTML5 trial on Youtube. After turned off flash player and took HTML5,  the videos on Udacity got better except for occasional latency.

So, if someone has the same problem on Udacity, you might resolve it with changing flash player into HTML5 on Youtube.