Low impact · weight 4 · worth up to 1.7 points of the total score
A missing or legacy doctype drops the browser into quirks mode, where box sizing and layout follow rules from the 1990s. The page then differs from every modern stylesheet assumption.
Make the very first line <!DOCTYPE html>.
Check a page for this, and the other 41 checks at once
Users can zoom the page
Disabling zoom locks out everyone who needs to magnify text. On modern browsers it buys nothing in return.
No deprecated presentational tags
Tags like <center> and <font> were removed from the standard. Browsers still honour them today, but they mix styling into the markup and no longer respond to CSS the way the rest of the page does.
Page declares a favicon
The favicon is how a user finds this tab among twenty others and how the site appears in bookmarks and history. Without a declared one the browser requests /favicon.ico and usually gets a 404.
Styling lives in stylesheets, not attributes
Inline style attributes cannot be cached, overridden by a stylesheet, or covered by a Content Security Policy that forbids inline styles. In quantity they also bloat every HTML response.
