Customizing HTML output 
  
  You can modify the look and feel of your HTML output by changing parameter settings
      to include custom CSS, headers and footers, or table-of-contents navigation in topics .
  
Setting parameters for custom HTML Customizing HTML with a .properties file .properties  file to reference a set of build parameters when     building output with the dita  command. The DITA-OT documentation uses a       .properties  file to include custom CSS, header branding, and table-of-contents navigation in     the HTML5 output.