Tidy is a commandline frontend to TidyLib which allows for cleaning up and
pretty printing HTML, XHTML and XML markup in a variety of file encodings. For
HTML variants, it can detect and report proprietary elements as well as many
common coding errors, correct them and produce visually equivalent markup
which is both compliant with W3C standards and works on most browsers.
Furthermore, it can convert plain HTML to XHTML. For generic XML files, Tidy is
limited to correcting basic well-formedness errors and pretty printing.