Why it's Important to Check for Penalties
A Google penalty is the negative impact on a website's search rankings based on updates to Google's search algorithms and/or manual review. The penalty can be an unfortunate by-product of an algorithm update or an intentional penalization for various black-hat SEO techniques.
If your website has been impacted by a Google penalty, your rankings and search engine visibility will drop, your website traffic will disappear and any sales you were making as a result of that search engine traffic will stop.
If your website traffic has suddenly stopped, then it's important o determine if a Google penalty, whether an algorithmic penalty or a manual penalty was the cause, otherwise no amount of marketing or promotion will improve your traffic unless it is addressed.
This video will show you how to do a quick check to see if you have in fact been impacted by a penalty.
For a more comprehensive investigation of the various types of penalties and how to address them check out this guide from Quicksprout.