There are a couple of signs which will alert you, which probably indicate that your website might have been banned. - A drastic drop in the number of visitors or queries or in final sale or your website pages not being indexed in Google. There are several factors, which forces Google to ban your site. Following are some such factors that may cause this banning.
The first and easiest way to get your site banned in Google would be to exchange links with banned websites like the ones dealing in free-for-all link sites, adult sites, or gambling sites. You should not spread viruses or Trojans to destroy users’ computers as well.
Stay away from a group of web sites where every site is hyperlinked to the other. They are generally created either manually or with autoprograms to spam the index of a search engine. This is known as spamdexing and also as Doorway Pages. Shy away from those which generate thousands of back links everyday for you - this alerts Google to ban your web site.
If you stuff your content with keywords or try to deceive Google using black hat software, your site will be banned too. On the contrary, you should try to optimize your site to earn the ranking and not stealthily with a software. As a general practice, keep out of every method that looks unethical.
Black hat software creates web garbage and in turn affects the performance of the search engine. As the sites are manually scanned in Google, if you do not have objectionable content or spam, your site will not get banned even if your competitors complain against your site
Putting too many keywords in the meta tag can also lead to banning of the site in google
Cloaking is another method that forces you web site to be banned by google. In this, a particular website returns changed web pages to the search engines to get better rankings. With cloaking you can hide the information of the page where even the HTML source code is not visible
If you submit multiple URLs from the same site that leads to two search results for the same page, your site will be banned as you tried unethically to manage more than one rank
Google strictly prohibits sending automated queries without express permission. Queries regarding page ranks or meta-searching etc., are never entertained by google
There are some technical criteria, which can lead your site’s ban in google. If the robot.txt file is changed to prevent search engines from entering your site or if meta tags direct the search engine robots to exclude your site, your site will be banned automatically
If multiple websites have same content in them, all of these sites may be banned by google. It is necessary for you to ensure that no other web sites are copying your content
Buying links in websites that are completely irrelevant to your business domain may not ban your site, but it will certainly result in poor page ranking. There are options for google to put your website in pending or halfway for 6 to 8 months so that you do not get the benefit of buying those links
There are stringent guidelines laid by Google which should be followed however to earn the page ranking. If you knowingly or by mistake disobey any of these guidelines, your page will be banned forever. Though Google has a resubmission option for including your website again, it may not be easy. The best method would be to maintain an ethical practice to provide the end users with valuable information and services