The Link Checker scans the site to find any broken links. Broken links are both bad for usability as well as can damage SEO rankings if there are too many broken links within the site.
On the top menu when logged in, go to: More > SEO Manager > Broken Link Checker tab.
A summary of broken links will display by page. Clicking each of these will expand the page to show all the broken links within that page.
Try using searching below: