To verify that you have the necessary prereqs installed, execute:

  rake prereqs

Information on the various requirements:

  Addressable:
    gem install addressable

    For best resuts, also install idn:
      gem install idn

    To make sure that gems are searched:
      export RUBYOPT="-rubygems"

  Html5:
    There was a bug fixed on 2007-12-09 that Mars depends on.  For best
    results, check out the latest:

      svn checkout http://html5lib.googlecode.com/svn/trunk/ html5lib
      export RUBYLIB="/path/html5lib/ruby/lib"

  XmlParser:
    Mars needs a *working* XML parser (REXML version 3.1.6 won't do).

    To determine the version of REXML you have installed:
      ruby -rrexml/document -e 'p REXML::VERSION'

    For best results (speed, spec compliance), install one of
      http://www.yoshidam.net/xmlparser_en.txt
      http://libxml.rubyforge.org/

    The latest REXML can be obtained by
      svn co http://www.germane-software.com/repos/rexml/trunk/ rexml
      export RUBYLIB="/path/rexml/src"