Great Product Rated 4 out of 5 stars

POSITIVES
Simple, clean, reliable tool to check whatever page you want, probably ones you're designing and want to catch your own coding mistakes, etc.

NITPICKY NEGATIVES
Gets an 8/10 only because I wish it did an easier check on my own bookmarks. It can do a less-seamless job if you export your bookmarks to a file, then check THAT page for dead links. An extra step, but it gets the job done.

OVERALL
A useful add-on, I'd recommend it.

This review is for a previous version of the add-on (0.6.1).