For example, had I performed a WHOIS lookup and found a bunch of porn or casino sites, I could have assumed (probably quite rightly) that Google had greylisted or blacklisted that IP address because of the sites hosted on it. Then, any legitimate site would also suffer the flag, causing indexing problems by the engine.

But that wasn’t the case here. As I said, it was a single site on a unique IP address.

I gave the information about the DNS to the site owner, indicating my concerns that the site wasn’t properly resolving and I found out a few days later that one of the hosts name servers was indeed acting up. I don’t know what “acting up” means, but it could indicate that the resolver wasn’t always resolving the IP to the site for some visitors, or it was improperly resolving it. In either case, should a search engine come across such inconsistency it will, over time, quit coming to the site.

More issues which could affect rank

There are other issues, not DNS related, but server related which could affect your indexing and ranking possibilities. These include improperly configured servers, or overloaded servers among other things.

Improperly configured servers

As you read above, there was an improperly configured (or failing) name server causing problems with the site, but there are other server issues which could affect the site as well.

Once the site is resolved via a name server, the request is then forwarded to the webserver hosting the site. If the webserver isn’t properly configured however to accept the request, then it will deny the request to the site, even if the site exists on the server.

While this is a rare occurrence, it does happen. If the webmaster mistypes the domain name for example, or attaches the site to the wrong IP attached to a different server, this could cause issues.

Another example of an improperly configured server is one which denies requests to domains without the “www.” Your webserver should be configured to accept all requests for a domain whether they have the www or not.

In fact, the ideal situation is for the server to automatically issue a “301” server site redirect to any request made for a non-www domain which then forwards users to the www domain. This is because sometimes search engines will see the www and non-www domains as 2 separate sites. Therefore link popularity and rankings could be split among the domains. In a worst case scenario, one or both of these domains could be banned by the search engines for duplicate content.

In addition, if you are fortunate enough to have your own IP address, you should check with your web host to ensure that the IP address resolves to the site. This way if a user (or search engine) tries to connect to the site via IP they will be served the site properly, and not receive a “page not found” error.

Alias issues

As mentioned above, it is best to have an non-www requests 301 redirected to the www domain. However, for ease of use (and because its quicker and easier to configure) most web hosts will allow all requests to a site to return that site, so that any request to the www, or non-www domain will return the same site. As I eluded to earlier, this could get the site penalized or banned. At the very least, the site won’t properly propagate link popularity, which will ultimately affect its ability to rank competitively in the search engines.

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