Planetmath.org is built with the following tech stack:
Document Standards
Javascript Defer
The defer attribute gives a hint to the browser that the script does not create any content so the browser can optionally defer interpreting the script. This can improve performance by delaying execution of scripts until after the body content is parsed and rendered.
HTML5 DocType
The DOCTYPE is a required preamble for HTML5 websites.
HTML 5 Specific Tags
This page contains tags that are specific to an HTML 5 implementation.
Content Type Options
Used to disable MIME-sniffing for a particular HTTP response.
Strict Transport Security
The HTTP Strict-Transport-Security (HSTS) header instructs the browser to only use https.
SSL Certificates
HSTS
Forces browsers to only communicate with the site using HTTPS.