Security
I use no Javascript at all.
I use no forms at all.
I use no cookies, other personal data storage, or tracking at all.
Efficiency
I use vector graphics whenever possible even for photos and have them compressed statically.
I have attached qr codes to my documents designed to be printed for easy return to the website.
Disability
I use structured documents for all webpages and ePubs as well as PDFs meant for screen reading.
I make full use of display type media queries.
I validate page structure for errors when making changes to it.
I do not interfere with keyboard accessibility.
I allow zooming.
I make accessible elements available for all users.
International
I use logical properties so my spacing is writing direction agnostic.
I have the correct page (human) languages marked correctly.