You have to access the websites by domain name. So to acchees them, oben a webbrowser and type the domain name into the URL field and hit return. You can not access the sites by entering the path on the harddisk into the browser URL field.
Regarding the FTP users:
1) Are there any jobs left in the jobqueue in the ispconfig monitor?
2) And are there any errors in the system log in the ispconfig monitor?
3) Which tutorial did you use to install the server?