You can preview your site from Plesk by clicking on the Site preview button inside the domain. Your site preview link is: http://server_IP/$sitepreview/domain.com/
Where domain.com is your domain and the server_IP is the IP of your server.
In order to preview your your domain in linux, please type in address bar of your browser:
In order to preview your your domain in windows server (WSP/DNP), please go to DOMAIN, click on CREATE INSTANT ALIAS and then click on the newly created domain alias.