Low impact · weight 3 · worth up to 0.8 points of the total score
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.
Replace them with CSS: text-align, font-family, font-size, and their friends.
Check a page for this, and the other 75 checks at once
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.
Links that open a new tab use rel=noopener
A page opened with target="_blank" can reach back to the page that opened it and send it elsewhere. Current browsers assume noopener, but older ones and some in-app browsers do not, and saying it costs nothing.
Email addresses are not left for spam bots
Bots crawl the web collecting every address written in a page or a mailto: link, and those mailboxes fill with spam within weeks. A contact form, or an address the page assembles with a little JavaScript, keeps the inbox usable.
