One word of advice, wear pants. Seriously.
I heard - and this may just be one of those great urban legends - that a candidate or two who have done one of these online things dressed up the top half but were wearing shorts/nothing on the lower half, figuring the camera would only see the top side.
At some stage the interviewer asked that the interviewee gather a document and when they stood up to get it and not thinking first about it...boom...their lack of effort in dressing for the job cost them said job...
Again, maybe an urban legend but still a great story...
But really. Wear pants. Good luck!