How to check if a website has been Banned by Google

Question

if your website links to another site that has been blacklisted by Google this is bad for your ranking
Sites like onlinealley helps you to know if there're problems with a website you are linking to.
Does any Google API Exist .. or how are websites like this checking if a url is banned?
Are they checking the 'PageRank value' or something else?

Answer 1

first of all banned pages wont have cache

secondly the PR score would be 0 to be precise

if you search with sitedomain.com in google search nothing will  appear if its banned