Unused pins should not be left unconnected (or floating). Instead, they should be connect to Vcc or Gnd through a ~10K resistor. If there's no chance that an unused pin will ever be configured as an output, then it is safe to tie the pin directly to the appropriate voltage (Vcc or Gnd) without the resistor.
Please Note: Any unused inputs should be terminated to the appropriate voltage (ground or power).
Keywords: Unused, pin, T0, T2, timer, pull up, pull down, floating