+The makefile variable @code{QUIET_BUILD} may be set to @code{1} for a
+less verbose build output, just like for building the programs.
+
+@knownissues
+
+@code{-j} command-line option of @command{make} is unsupported for
+building the documentation. As the most time consuming task is
+running LilyPond to build images of music, the makefile variable
+@code{CPU_COUNT} may be set in @file{local.make} or on the command line
+to the number of @code{.ly} files that LilyPond should process
+simultaneously, e.g. on a bi-processor or dual core machine
+
+@example
+make CPU_COUNT=2 web
+@end example
+
+If source files have changed since last documentation build, output
+files that need to be rebuilt are normally rebuilt, even if you do not
+run @code{make web-clean} first. However, building dependencies in the
+documentation are so complex that rebuilding of some targets may not
+be triggered as they should be; a workaround is to force rebuilding
+by touching appropriate files, e.g.
+
+@example
+touch Documentation/user/*.itely
+touch input/lsr/*.ly
+@end example
+