Keys:

When viewing a host, you can move the map around and zoom in and out with your mouse. You can follow specific racers around the track by clicking on their names in the racer list to the right. Double click to zoom in. Clicking their position button shows a racing line, which might help tracking them.

For many of the button-options you see there are also key shortcuts :

'TAB' / 'Shift-TAB' to cycle through the racerlist
'f' to go to Full Screen mode
'F' to show / hide all text
'n' to show / hide names
'h' to show / hide the message history
'l' to show the list of hosts
+/- to zoom in and out
Arrow keys move the map
Space-bar hides the options list
ctrl-shift shows usernames (on licensed hosts)