Bad neighbourhood is an anglicised spelling of a phrase which is most often written in the American fashion, like Bad Neighborhood (minus the letter “u”) because its a phrase relating to SEO in the sense that you can (more, could, in the past) become associated with “bad stuff” which exists online.
The theory was – and this was true – that bad things sitting on an IP address, or hosted in a certain place, could de-rank other websites which were sitting on the same infrastructure.
Similarly, sites which link to bad apples – routinely – or in a network, may get associated together and also become a “bad neighborhood” – though it should be noted that the phrase originally was used in the first context, above.
This concept led a little to revenge SEO and aggresive tactics like over optimizing competitor’s websites, and Google (etc) have become way more sophisticated than thinking that things on the same IP address are necessarily associated.
Bad neighborhoods aren’t such an issue in 2018, therefore, but you should still try not to be associated with… well anything spammy or using “cheating” tactics when it comes to your website. If it is black or grey, and it works today, you may be storing up problems for yourself in future.
Please your users, with your website, and make your site reflect what they want to see, and you’ll rank in search engines. Its about relevance.
But for everything else, there is structure, speed, and other technical things you can do to completely fairly optimize your website to please users – and consequently search engines. For all those things, contact Silicon Dales, who can get your site really tuned up for the top of SERPs!