In general, PDFreactor was designed for the printing of valid XHTML and XML content using CSS to control the layout. PDFreactor does provide clean-up processes which enable it to convert invalid legacy HTML code to valid XHTML before printing. Thus, you can even use PDFreactor to print legacy HTML code, as long as the clean-up process is able to handle it. However, some legacy pages contain errors which can not be handled by the clean-up process.