Link rot is one of the web's quietest problems. Pages disappear, URLs get renamed, external sites go offline, and your once-working links slowly turn into 404s — damaging your SEO rankings, frustrating visitors, and leaking link equity to nowhere. These guides cover how broken links happen, how to find them systematically, how to decide which ones to fix first, and how to prevent new ones from creeping in as your site grows. Written by developers who audit client sites for a living, and focused on practical fixes rather than generic "you should probably do this" advice.