Many sites vary their content or style or both based on the “maturity” of the user and acceptability of “mature content” in their browsing environment:
- Sites for children have parent sections or modes, where the style may be less playful and concentrate more on dull (and smaller) text than on colorful graphics. Typography may be adapted accordingly to aid either reading many paragraphs or deciphering a couple of words.
- Entertainment sites are tagging delicate (user-generated) content as not safe for work (NSFW) and let users either opt-in or opt-out to access it.
- Search engines offer a safe mode for content that may be offensive, often with three levels: on, moderate, off.
- Several countries require age verification (by various methods) for some content or only allow it during specific local times (i. e. usually during childrenʼs nominal bedtime).
- Many countries have voluntary or mandatory content rating systems (issuing labels) or even censorship agencies (altering or restricting content) for graphic, lyric or interactive content, but exact age groups and criteria depend a lot on culture and tradition. Beeping over curse words, blurring genitals or replacing Nazi symbols belong in this category.
- “Adult” sites, i. e. porn in most cases, hide or obscure hardcore content from guests, i. e. possibly underage, unverified visitors that are not logged-in paying members.
- If known, some styles are also varied with the userʼs gender, e. g. pastel colors and cursive fonts for girls vs. earthen tones and stencil lettering for boys.
- Parental controls and company policies may use filters, whitelists or blacklists to restrict or prohibit user access to certain content or sites.
Iʼm not sure whether or how MQ should address this. I tend to think it is in scope. This is a sensible topic and usually has less or no effect on style in comparison to content, but Mediaqueries are not limited to selecting stylesheets anyway.
Authors might want to know the exact age (at least with year precision) of the user to determine appropriate style and content, but birthdates are not usually collected by OS and browser, so arenʼt available at all, and even if they were they would probably be unreliable and should not be reported in detail for privacy reasons.
However, an age group or related social role could possibly be determined implicitly or selected explicitly. Possible values could include:
The user environment could be derived from some parameters that may be available to the browser or at least to the operating system. Possible values could include