Troubleshooting

Make sure you restarted Firefox or Thunderbird, and either restarted Chrome/Safari/Opera or reloaded your webmail page.

Switch your "Syntax Highlighting CSS" theme in the MDH Options.

syntax highlighting theme change

MDH doesn't automatically update your Primary Styling CSS if the default changes (issue #48), so you'll need to manually reset it.

primary styling css reset

Reporting and Debugging

copy html in Chrome

Copy HTML in Firefox

inspect background scripts in Chrome