I have heard a lot that giving link to a bad neighbours can result in Google search penalties. But never understood how to identify the bad neighbours?So please if anybody can help me and explain this. And also if you are linking to a bad neighbourhood sites,but getting a backlink from such a site,can this affect your pagerank or rank in Google search indexing?
Bad neighbour sites are often spam sites or sites with blackheat seo techniques. Often the site will be a place where you don't want to be and it often looks not really trustworthy. In my opinion are the following sites in bad neighbourhoods. -Linkfarms -gambling sites with many pop ups and unwanted ads. -s#x sites of course Actually every 18+ sites are sites that google don't want in the serps. So don't link to them unless it has the nofollow tag. And if you get links from those sites it wont hurt, because Google know from the past that some people applied negative SEO to penalize the competition by giving them 1000ts of bad neighbourhood links to let google know the site is also bad. So if you have many badneighbourhood links it won't hurt, may even be a little bit beneficial. But don't link back, if it is not necessary, and if it is, than put the nofollow tag on the link or even make a javascript link, which googlebot can not (yet) crawl.
In addition to what rruben said, I read somewhere bad neighbor also include sites that got penalized for good. So if you see the sites is quite old but not in google index, better use nofollow or simply don't link to them. Tool to check before you link to a site: http://www.bad-neighborhood.com/text-link-tool.htm
Bad neighbours include MFA's, Spammy, keyword stuffed sites and link farms. Definitely not made for the reader. Use your common sense- you'll understand whether a site is good or bad when you visit it. That is the best way of identifying one.
Also another good bad neighbors tool but different is: http://www.myipneighbors.com/ It will show all the sites sharing the same server as you, and also you can view all the sites. It's also is good to see if your host is overloading the server.
Getting a link from a bad neighborhood of the web won't hurt you, unless the vast majority of your links come from these sites.
It really just depends, a single domain can bring a Quad Core server to it's knees or you can run 1,000 static HTML sites on the same server and it not break a sweat. The best way if you are on a server, is to check the CPU load and RAM usage. This tool is a good indication when you are choosing a host to see how loaded up their servers are before purchasing as well as seeing what types of sites they host.