  The fine structure and the variations of the optical pulse shape and phase of
the Crab pulsar are studied on various time scales. The observations have been
carried out on 4-m William Hershel and 6-m BTA telescopes with APD photon
counter, photomultiplier based 4-channel photometer and PSD based panoramic
spectrophotopolarimeter with 1$\mu$s time resolution in 1994, 1999, 2003 and
2005-2006 years. The upper limit on the pulsar precession on Dec 2, 1999 is
placed in the 10 s - 2 hours time range. The evidence of a varying from set to
set fine structure of the main pulse is found in the 1999 and 2003 years data.
No such fine structure is detected in the integral pulse shape of 1994, 1999
and 2003 years.
  The drastic change of the pulse shape in the 2005-2006 years set is detected
along with the pulse shape variability and quasi-periodic phase shifts.
