This is the Mavo website repo. For the Mavo repo go to https://github.com/mavoweb/mavo
Before editing any HTML files, check if there's a .tpl.html file with the same name in the same folder. If so, it means that the corresponding .html file is generated, so you want to edit the .tpl.html instead (and don't forget to run gulp watch before edting OR gulp html after editing!).