Free link checkers: W3C and Xenu
I’ve been using Xenu Link Sleuth (free) to check for broken links. I also use the output report to review web page titles (which are displayed as links in most search engines) and to produce a list of valid links for use with the batch mode of the WDG HTML Validator (100 URLs at a time).
I knew W3C had an Markup Validator and a CSS Validator, but was unaware of the W3C Link Checker until now.