  HQM is an optical broad-band photometric monitoring program carried out since
Sept.~1988. Our main intention is to search for indications of microlensing in
a sample of $\sim$\,100 selected quasars; however, we also want to study the
intrinsic variability. We use a CCD camera equipped to the MPIA 1.2$\,$m
telescope. Fully automatic photometric reduction relative to stars in the frame
is done within a few minutes after each exposure, thus interesting brightness
changes can be followed in detail. The typical photometric error is 1--2\,\%
for a 17.5\,mag quasar, making HQM the most accurate long-term quasar
monitoring program yet carried out. The main results of HQM which we discuss
here are: (1) Concerning variability, quasars form two, clearly distinct
classes, optically violent variables (OVVs) and non-OVVs. (2) All OVVs are
radio loud and probably belong to the blazar class. (3) Non-OVVs have
lightcurve gradients of at most several 0.1\,mag\,yr$^{-1}$ in the quasar
restframe and can be well fitted by polynomials of low order. (4) Although our
data cover only a relatively short timespan, we conclude that there is a large
fraction of quasars which would be undetectable in photographic surveys using
optical variability alone as the selection criterium. (5) A broad class of
flat-spectrum radio quasars are no blazars, they are even less variable in the
optical than radio quiet objects. (6) There is some statistical evidence for
microlensing in our sample; if present it does, however, lead only to low
lightcurve gradients.
