"validate", the Offline HTMLHelp.com Validator, checks the syntax of HTML
documents using an SGML parser and reports any errors.  XHTML documents
may also be validated using an XML parser.

Usage: validate [OPTION] [FILE...]
        
The program's options are as follows:
  -w, --warn                  include warnings
  --xml                       indicate that the documents to be validated are
                              XML documents.  Known document types, such as
                              HTML 4.01 and XHTML 1.0, are automatically
                              handled by "validate".  For unknown document
                              types, "validate" will assume XHTML/XML if this
                              option is specified and HTML/SGML otherwise.
  --header='Name: value'      set an HTTP header for HTTP requests (may be
                              used multiple times for separate headers)
  --charset=ENCODING          force ENCODING to be used as the character
                              encoding when validating HTML/SGML documents.
                              This option is ignored when validating XHTML/XML
                              documents, which are assumed to use XML rules for
                              specifying the character encoding.  The following
                              encodings (case-insensitive) are supported:
                              "utf-8", "iso-10646-ucs-2", "euc-jp", "euc-kr",
                              "gb2312", "shift_jis", "big5", and "iso-8859-n"
                              where n is between 1 and 9 inclusive.
  --verbose                   turn on verbose output messages
  --[no]emacs                 (don't) use an output format intended for parsing
                              by (X)Emacs, autodetected
  -h, --help                  display this help and exit
  -v, --version               output version information and exit

Any number of files may be specified after the options.  With no FILE,
standard input is read.

Files can also be URIs if you have the URI and libwww-perl packages
installed.  Support for different URI schemes is also determined by these
packages.  Proxy settings are loaded from environment variables for
each scheme--e.g., http_proxy=http://localhost:3128.

"validate" is written by Liam Quinn <liam@htmlhelp.com> and is based on the
WDG HTML Validator, an online validation service available at
<http://www.htmlhelp.com/tools/validator/>.