Why Google Rankings Drop

There are several reasons that can cause a ranking drop on major search engines, some of them are listed below.

• Whenever you change your web pages or do any major updations on your website, Google temporarily downranks web pages.You don't need to worry about the ranking drop as you'll get your old rankings back after some time.
• As your competition keeps on growing so might be other web pages are better than yours. In that case, optimize your web page for more targted keywords and try to get more better inbound links.
• Google might think that you are using spam elements on your webpages you can find out if your website has been penalized or not. Search for your domain name on Google, if Google
  cannot find any page of your website if you search for "site:yourdomain.com" then it's nearly sure that your website has been penalized.