Simple Question About The Interactive Demo: HTML / JS Rookie Help

In the interactive demo, you have to press the START button. When I try to modify the coding to automatically start when the page loads (for example button("startBtn").click() sort of. ) Everything I try starts it up, but the A/V doesn't show up? Can anyone tell me what I am doing wrong, I would say that the media part starts up in the wrong order or something. I know, it is a rookie question but ....

Thanks in advance for any advice (other than take a HTML/JS coding class :) )