This is the last part of the series. You have chosen a domain and host, fixed the install settings, picked a theme and plugins, built pages, registered with search engines and set up a mail path. One last pass before you open.
The order matters below: each stage is arranged so that a failure earlier makes the later checks meaningless.
Stage 1 — does it open?
Watch for mixed content in particular. If SSL is on but the padlock does not appear, something on the page is still loaded over http:// — usually an image or a script. The browser console flags it.
Stage 2 — can search engines see it?
The first line of this stage is the single most important line in the whole series.
Stage 3 — do enquiries arrive?
Submit the form yourself. Send a test enquiry and check both the inbox and the spam folder. If it lands in spam you can still open, but revisit your domain authentication records.
If you configured an auto-reply, read it once. It is the first mail a customer receives from you.
Stage 4 — be ready not to lose anything
Take a backup of files and database together right before launch. If you can, restore it once somewhere safe — a backup you have never restored is not a backup.
Finally, tidy the accounts: temporary administrators from the build, test users, plugins you no longer use. Changing the password once at this point is worth it too, since it has probably been shared around during the build.
Closing the series
If you have followed this far, you have what you need to open a business site on your own. From here you accumulate content, take enquiries, and add things as the need appears.
When you get stuck in operations, the development workflow archive is a good place to look; and for the work that is genuinely hard to do alone — version upgrades, performance work, security review — our optimization program handles it as one job. How we work is published step by step on the process page.