In most cases, it is easy to detect if Google issues a penalty to our website. But in other cases it's difficult to detect. Hopefully the few hints below tell us that our site might be getting that dreaded penalty from Google.

Assuming my website is www.website.com,
 

1. Check how many pages are indexed

You can check this one by entering site:website.com in Google search engine. if the resulting number of pages is zero, it's a big indication your site is banned by Google. But it's also possible that you may have restricted access of crawlers (using noindex, nofollow or blocked crawler entry using robots.txt).
 

2. Check your brand name as search query

If I search for "website" and the page I expected does not show up, it's not a good sign.

3. Check your browser's PageRank toolbar value

Typically it shows a strip of green. But if it turns gray, Google may have ignored its PageRank value and your site could be in trouble.

4. Check your visitor traffic source from search engines

Using your favorite web analytics tool, you can check whether your website's traffic from search engines have suddenly dropped. This could be caused by drop or disappearance of your site on search result. That is a red flag that could indicate search engine penalty. If you are convinced that your website has been penalized, spend time on reviewing Google's own advice (look no further) on SEO help for webmasters.

Photo credit: keso