Unknown notifications I'm receiving time to time the notifications as shown on this screenshot.



The notifications are on the top right of my screen.

I can't understand the origin of these notifications thus I don't know to disable them.

What are they and how to disable them?
You're receiving push notifications from specific websites. Here's how to block them in Chrome, from Google's support page.


  Allow or block notifications from all sites
  
  
  Open Chrome.
  In the upper right corner of the browser window, click the Chrome menu Chrome menu.
  Click Settings > Show advanced settings.
  In the "Privacy" section, click Content settings.
  In the dialog that appears, go to "Notifications" and choose one of the following:
  
  
  Allow all sites to show notifications: You’ll automatically see notifications from all websites.
  Ask when a site wants to show notifications: You’ll get an alert from Chrome whenever a site wants to show you notifications. This is the default setting.
  Do not allow any site to show notifications: You won’t see any notifications from websites.
  You can also block any sites, apps, and extensions that already have permission to send you notifications. Just click Manage exceptions.
  
  
  
  Turn off notifications from some sites
  
  
  At the top of your screen in the menu bar, click the notification icon [which looks like a bell].
  Click the gear icon.
  Uncheck any website, extension or app you don’t want to receive notifications from.