The base URL is, http://brock-family.org/youtube.html however you can control it by passing arguments at the end of the url:
mute=1 – Turns off the sound (usually a good idea)
rows=n – Sets the number of rows of videos to view. n can be any number that your system can handle
cols=n – Sets the number of columns of video. Again – limit is up to your system
For example – my favourite is 3×2 videos with mute:
One other feature – if you only have 1 video (rows=cols=1) then the page will use a cookie to remember your last position in the last video.