This is a JugglingLab simulator and is free for non-commercial use.
If You can't see any juggling after You've pressed the juggle button (or even there is no button) then You probably don't have java installed.
You can get it here.
More about siteswaps You can find in siteswap section.

If you want to watch every single ball, you can color balls differently by adding this to the "manual settings":
colors = {red}{yellow}{green}{blue}{pink}{cyan}{black}{gray}{magenta}{orange}