  A new generation of parton distribution functions with increased precision
and quantitative estimates of uncertainties is presented. This work includes a
full treatment of available experimental correlated systematic errors for both
new and old data sets and a systematic and pragmatic treatment of uncertainties
of the parton distributions and their physical predictions. The new gluon
distribution is considerably harder than that of previous standard fits.
Extensive results on the uncertainties of parton distributions at various
scales, and on parton luminosity functions at the Tevatron RunII and the LHC,
are obtained. The latter provide the means to quickly estimate the
uncertainties of a wide range of physical processes at these high-energy hadron
colliders, such as the production cross sections of the $W,Z$ at the Tevatron
and the LHC, and that of a light Higgs.
