generate.css.header boolean generate.css.header Insert generated CSS styles in HEAD element The stylesheets are capable of generating both default and custom CSS stylesheet files. The parameters make.clean.html, docbook.css.source, and custom.css.source control that feature. If you require that CSS styles reside in the HTML HEAD element instead of external CSS files, then set the generate.css.header parameter to nonzero (it is zero by default). Then instead of generating the CSS in external files, they are wrapped in style elements in the HEAD element of each HTML output file.