I have already read:
Novell Documentation
Setting up SSL: Ubuntu and Apache 2
How to install iFolder on Ubuntu server « x2b4

I've installed iFolder and certificates according to these sites, but when I enter

where is IP of my server, I receive:

Internal Server Error

The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator, webmaster@localhost and inform them of the time the error occurred, and anything you might have done that may have caused the error.

More information about this error may be available in the server error log.
OS: Ubuntu server