We User are like FTP user you can use this as individual FTP account and you can host on your Web server personal Web pages for individuals who do not need their own domain names. These pages usually have web addresses like http://yourdomain.com/~username, however, you can set up personal web pages with alternative web addresses like http://username@yourdomain.com, if you like.

Login to your Plesk Control Panel  under the Website menu click on Web Users.

Now click on Add New Web User.

Now need to create your Web User with require details (User Name, Password, Disk Quota and necessary support) and then click OK to save the changes.

Web user has been created.To view list of web users go to Home and click on "Webusers" under Website menu.

 Don't Forget to Logout when you are done.