Test your installation by typing command:
  javac
This should display help on the java compiler options.
Basically you unzip the file into a directory and add an ANT_HOME environment variable that points at it. Test your installation by typing the command:
  ant -help
This should display help on ant options.
The unit test code relies on lib/junit.jar from the JUnit project. The version used on the build machine is 3.8.1 which you can get here.
Unjar this file with the command:
  jar -xf src.jar
There should now be a build.xml in the top level directory.
  ant
If you just want to build some of the parts see the help list:
ant -projecthelp
 Package        glom the release and source files into the distribution zip file
 Release        prepare the release files
 changelog      create the change log from CVS logs
 checkstyle     check source code adheres to coding standards
 clean          cleanup
 compile        compile all java files
 compilelexer   compile lexer java files
 compileparser  compile parser java files
 htmlparser     same as Package plus cleanup
 init           initialize version properties
 jar            create htmlparser.jar and htmllexer.jar
 jarlexer       create htmllexer.jar
 jarparser      create htmlparser.jar
 javadoc        create JavaDoc (API) documentation
 sources        create the source zip
 test           run the JUnit tests
 thumbelina     create thumbelina.jar
 versionSource  update the version in all java files
  
junit.jar file from the lib directory, and the
  tools.jar file from the java JDK lib directory
  [where java is installed]/lib/tools.jar. "Build All" should work.
  CVS
  The most recent files are only available via CVS:
  
  server: cvs.htmlparser.sourceforge.net
  repository: /cvsroot/htmlparser
  
  For read-only access use 'pserver' and anonymous access with no password.
  For commit access you'll need to set up ssh (see 
an
introduction to SSH on sourceforge and 
a
guide on setting up ssh keys).
Short instructions from Karle Kaila:
I have installed SSH software from www.f-secure.com
I think it was something like F-Secure SSH 5.2 for Win95/98/ME/NT4.0/2000/XP Client
It is a nice grapfical SSH client both for terminal use and filetransfer
and it also contains commandline ssh2 software that CVS needs.
To access CVS I first set it up with these commands
set CVS_RSH=ssh2
set CVSROOT=username@cvs.htmlparser.sourceforge.net:/cvsroot/htmlparser
username = your sourceforge username
In an empty directory I then can give CVS commands such as
cvs chekcout htmlparser
It asks for your password to sourceforge
This retrieves the latest  fileversions.
Check the CVS commands in some handbook you can find on the internet.
The manual I found is called Version Management with CVS by Per Cederqvist et al.
perhaps from http://www.cvshome.org
Derrick says:
I need
CVSROOT=:ext:username@cvs.htmlparser.sourceforge.net:/cvsroot/htmlparser
CVS_RSH=ssh
  Other
  Some of the build.xml targets (like changelog) rely on Perl to execute, and
  need a sourceforge login via ssh (secure shell). This is unlikely to be needed
  by the casual user.