If you’re wondering whether your site might have been banned or penalized by the search engines, it can be difficult to tell. The SEs generally don’t display anything publicly to state a site has been banned or penalized. You can check this for yourself by looking at the SE results for competitive search terms. Honestly, I spend a lot of time searching for one thing or another, and I don’t think I’ve ever seen any sort of notification like that. Ever.
Google will sometimes alert a site owner there is a problem through their Webmaster Tools. That, and the fact that the Tools give a lot of good information about how Google views your site, makes it well worth signing up for the Tools and validating your site(s).
But in general, they don’t tell you that you’ve been penalized. If the SEs told everyone when they’d been penalized, and exactly what it was they’d done to earn the penalty, it would only make it easier for SE spammers to do an end-run around the SE algorithms. So it’s to the SEs’ benefit to keep things as vague as possible. Frustrating for the site owner, but there’s not much to be done about it.
Bans vs. Penalties
There’s a whole range of things the SEs can do to sites that engage in practices they don’t like. In the very worst cases, they can ban the site — i.e. drop it from their results entirely. This is very, very rare, and generally only happens when someone’s been extremely naughty.
For lesser infractions, they could penalize the site. There are a whole bunch of penalties they can apply — from simply indexing the home page and ignoring the rest of the site, to listing all the pages of the site, but only displaying them toward the very end of the results, to knocking the pages of the site down slightly in the results for certain specific search queries. Basically, what penalties they might choose to impose are up to them and limited only by their imaginations, the laws of physics, and corporate policies.
However, in many (most?) cases of suspected penalties/bans, it turns out there are technical issues (malformed robots.txt file, unspiderable site navigation, required cookies or sessionID, etc.) — or in Google, simply the normal aging delay for new sites — that are causing the problem. They may look very much the same as a penalty or ban in the results, and it’s often difficult to determine what’s really going oin without a bit of investigation.
Another common cause of poor ranking is — and how shall I put this delicately? — (ahem) "overly optimistic" evaluation of the webmaster’s site optimization skills. I can’t begin to tell you how many times on the High Rankings Forum we get pleas for help from webmasters who swear their sites are "fully optimized," have no technical difficulties, and yet are still not indexed well. And, of course, their immediate thought is that a penalty or ban for "over optimization" must be in place.
The problem is, usually within a few minutes (often within a few seconds) of visiting their site, we can all identify many areas that have not been "fully optimized." It generally becomes apparently fairly quickly why these sites are doing so poorly in the search engines.
As with banning, penalties are generally fairly rare (although not as rare as an outright ban), so when a site isn’t performing as well in the SEs as we’d like, generally it’s best to first look for technical issues and make sure everything is squeaky-clean in that respect. All too often, site owners jump to the conclusion they’ve been banned or penalized when the problem is actually a technical issue on their site — which could be very easily resolved.
The second thing to do is to honestly take a look at the site optimization. As a site owner you might want to take a look at this excellent thread at the HighRankings.com forum to learn more about what really works for site optimization.
The SEs don’t go around handing out penalties like candy. You generally have to have done something pretty seriously bad to earn a penalty, and generally site owners who get penalized know just what they’ve done (whether they choose to admit it publicly or even to themselves is another matter).
Bottom line: it’s usually fairly difficult to accidentally incur a penalty or ban. Not to say that it can’t be done, but — like penalties and bans themselves — accidentally getting in trouble with the search engines is rare. If you’re having trouble, it’s much more likely either a technical issue or simple poor optimization to blame.