Useful, could do more Rated 2 out of 5 stars

Works for page not found errors, but does not work for couldn't connect to host errors. Now I have to try all the competing extensions!

Also, the popup is a bit annoying, hacking the button inside the page with error or as an overlay for the page with error would be way more cool.

This review is for a previous version of the add-on (1.2.1). 

good suggestion

thanks for suggestions. will try to add host errors for next version. in the meantime, you can use 'archive' button that you can place on the toolbar. when you click on it, you will see archived page.

i agree that popup can get annoying if many error pages are encountered in a short time, but won't be fixing that for a while as it doesn't happen that often to me :P