Low impact · weight 1 · worth up to 0.3 points of the total score
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.
Replace the address with a contact form, or put it together in JavaScript so it is not in the HTML as one string.
Check a page for this, and the other 70 checks at once
Viewport meta tag is present
Without it mobile browsers render the page at desktop width and shrink it to fit, which fails Google's mobile usability bar and leaves text unreadable on a phone.
HTML parses without errors
Browsers repair broken markup silently, and each one repairs it slightly differently. Unclosed and misnested tags are where a layout that works in one browser collapses in another.
Element ids are unique
An id must appear once per document. Duplicates break label-to-input pairing, in-page anchors, and any script that looks an element up by id, and every one of those failures is silent.
Page is served over valid HTTPS
Browsers mark plain http pages as not secure, and an expired certificate replaces the whole page with a warning that almost nobody clicks through. Certificates now last 90 days or less, so a renewal that silently stopped working takes a site down within weeks. Protocols older than TLS 1.2 are refused by current browsers.
