Google Detached Retina How Do You Detach A Google Robot From A Picture?

How do you detach a google robot from a picture? - google detached retina

Recently I discovered that my Facebook profile image from Google Images. I searched on Google how to get rid of him, but I do not understand how.

To delete all images on your site from the index, and place the following robots.txt file in the root directory of your server:

User-agent:
Disallow: /

I do not understand where and when the root servers .... Please help:)