Maintenance page

[simonrjones]

Take site down and return static HTML page. Review best way to manage this.

Need a pre-prepared self contained HTML page.

Need to return a 503 status code and indicate when user should revisit:

header('HTTP/1.1 503 Service Temporarily Unavailable'); header('Status: 503 Service Temporarily Unavailable'); header('Retry-After: 1800');

Nice-to-have: open up site access to a set of IP addresses so we can test site without making it public.

See https://yoast.com/http-503-site-maintenance-seo/