Historical version. PostgreSQL 7.4 has reached end of support. See the current manual.
14.3. Getting The Source
The PostgreSQL 7.4.30 sources can be obtained by anonymous FTP from ftp://ftp.postgresql.org/pub/source/v7.4.30/postgresql-7.4.30.tar.gz. Use a mirror if possible. After you have obtained the file, unpack it:
gunzip postgresql-7.4.30.tar.gz tar xf postgresql-7.4.30.tar
This will create a directory postgresql-7.4.30 under the current directory with the PostgreSQL sources. Change into that directory for the rest of the installation procedure.
Report a documentation issue
Read the upstream documentation. For corrections, first check the current manual.