Check the recent HTML approved items. Get ideas from that. As @charlie4282 mentioned > With any HTML file you need to ensure best practice, no inline CSS etc., validated code, do not include any premium plugins, scripts, images etc. That you do not have permission and licenses to use or distribute, etc. Along with that comment each section so that buyer can get idea what is going on. It would be better if you can add different versions of homepage plus single page layouts.