Another thing you could do but might be inconvenient is to use the first page in the design for version/caching control while you're working on the site. So for example name your first page "sitev1" and then have the second page in the design as your index.html. Then when you publish the htm_files folder name will match the filename of your first page so it would be "sitev1_htm_files" and the next time you do a major update change it to "sitev2" which then would create "sitev2_htm_files". You wouldn't want to do it for minor changes but perhaps after a lot of major changes. This would avoid caching issues as all links to file assets would change to the new folder name. Note this wouldn't work with a site navbar set to link to all pages automatically and you would need to manually delete old htm_files folders manually after a while. Normally though I would just get into the habit of telling the customer to Ctrl+F5 to clear cache every time emailing them with significant changes, although if they are previewing on a tablet or mobile it's less straight forward digging around in various browser menus to clear cache.