LinkGuardian: Smart Link Checker od Kuwin Day

Verify and highlight broken links on web pages
Automatic link checking on page load (optional)
Custom highlight color for broken links
Export list of broken links
Scheduled link checking (daily, weekly, or monthly)
Keyboard shortcut (Ctrl+L) to start checking links
User-friendly popup interface with results display
Separate options page for advanced settings
Prevention of clicking on broken links with a warning message
Persistent settings across browser sessions