It is actually an add-on for firefox .

You just need to download optimize google add-on for firefox.

After adding this add-on to your firefox you are done and let this software to do it's work . I have an example image for it

You can easily filter your search results to see dead websites by using wayback machine

Way back machine is actually a software which let your browser to surf internet as it was before any changing

In the end i would like suggest you to use google suggested sites which make searching on this powerfull search engine easy.

Liked the post? 
Then subscribe to HT to remain updated.