Avoid Harmful Inbound Links to Your Web Site
Inbound linking to your Web site is generally a good thing — it tells the search engines that you have a vote of confidence in your expertness level — but some inbound links out there only hurt you in the long run. There are several kinds you should be on the lookout for: from non-harmful reciprocal links to the riskier incestuous links, link farms, Web rings, and bad neighborhoods.
Google can detect when you have bad links. They can take away the link’s PageRank as well as the link and domain equity/authority and won’t pass on any link value to your page. Google won’t count the bad incoming link, and if they suspect you’re doing something sneaky and devious with it, they even penalize you for it. The penalty could be as simple as removing all of the link equity of your site, or they could punish you by reducing your rankings on the results page. They may even remove your page or entire site from their index. Ouch!
Avoid reciprocal links
Reciprocal linking is the least worrisome of the bad inbound links. If a site links to you, and you give them a link back, that’s a reciprocal link. Unfortunately, doing this does limit the value of the link in either direction. Reciprocal links are bartered exchanges, so they might be treated just like an ad from a search engine perspective.
Avoid incestuous links
Incestuous links occur when people link to their own properties or among a group of friends' sites and then try to pass the links off as legitimate links from outside sources. If you have several sites, and they all link to each other, and you’re trying to pretend that you don’t own half of those sites, that’s some incestuous linking going on.
These types of links are called incestuous links because they are no good and should make you feel icky. Smaller sites caught using them are punished. When you are caught using incestuous links, not only do you run the risk of having those links devalued, but your site could also be marked as spam, and you may have all of your links devalued. And that’s not even the worst that can happen. When you get penalized for this type of spam, your site can vanish from the index altogether.
Avoid link farms
Search engine spam includes any sneaky, devious, or underhanded technique used to trick search engines into giving Web sites higher rankings. Link farms are literally pages of hundreds (or even thousands) of links on many sites that all link together. This is slightly different than incestuous linking as you might not own the properties involved. In general, you should be very suspicious if someone asks for a link from your site and offers you a link from a totally different site in exchange. That's a classic warning sign for a link farm.
Link farms are sites that have many different links to multiple different sites, all for the express purpose of passing link equity and giving those sites a higher rating in the search engines. Sometimes you can’t help it if a link farm links to you, however. If you discover that your site is part of one, politely ask for it to be removed as soon as possible. Being caught as part of a link farm could lead to all of your links losing their link equity or even harsher penalties.
Avoid Web rings
Web rings are not necessarily spam. Web rings are any collection of Web sites from around the Internet that join together through interlinking in a circular structure. When you join a Web ring, you are automatically part of a circle of related Web sites. You can tell a site belongs to a Web ring because they usually have a widget (an interactive piece of HTML coding) that looks like the following figure.
It’s pretty easy to identify whether you’re in a Web ring, as the presence of the widget is something of a clue. You probably shouldn’t join a Web ring because all of those links do not give you any link equity. On top of that, it probably isn’t worth the traffic you’ll be receiving.
Avoid bad neighborhoods
Sometimes a Web site is not part of the search engine’s index. It could be that the Web site is too newly created. But it is more likely that the Web site is from a bad neighborhood. This is a Web site that got yanked from a search engine index, and probably for a good reason. Either they were spamming or using other sneaky methods to try and fool the search engines, and they got caught.
Being part of a bad neighborhood or accepting links from a site that has been banished from the index is about the same as if you had suddenly associated with the bad kids at your high school. Your site gets flagged, and you come under suspicion of using spam techniques yourself.
If you catch any unsavory linkage from sites in a bad neighborhood, drop them an e-mail and ask for your site to be removed. Also, this is why you need to keep all things on your site above-board and clean — Google doesn't inform you if you have been flagged. They might send you an e-mail if you have Google Webmaster Tools, but otherwise, if you’re flagged and they discover anything wrong, you are simply punished.