If your requirement is that you want to be able to block a site and all it's pages entirely (e.g. example.com and example.com/a and example.com/b) I guess this works.

If -- like me -- your requirement is that you want to block the primary domain example.com but access links on same domain e.g. example.com/a/link/here.html it's unlikely to work, at least not without an enormous amount of frustration.

Also, the "save" button in the options need to be made much more visible.