Use AutoHotKey and the script below.

xmin = 150
xmax = 500
ymin = 150
ymax = 1000

Loop
{
IfWinExist, Google Zeitgeist 2013
{
WinActivate ; Automatically uses the window found above.
WinWaitActive, , , 2

random, nmx, %xmin%, %xmax%
random, nmy, %ymin%, %ymax%
MouseClick, left, %nmx%, %nmy%
Sleep, 6000
MouseClick, left, %nmx%, %nmy%
}

Sleep, 1500
}