website ban google

Hello guys, This is first time I experienced my site got deindexed from Google search. When I search "site:mysite.com" on Google nothing shows = Means deindexed. I made it before 5 months ago and it was ranked on 1st page of Google until today when it got de-indexed. I made just ONE backlink...

Hi, i got a google ban. My rankings dropped from 100 organic visitors from google to 3-5 a day. In google analytics i have no manual penalty. How can i know why google banned me? I have not used blackhat seo on that website. The url is: http://beleggersforum.net ,it's a Dutch forum.