If you are a Webmin/Virtulamin server administrator and have received this error, one place to start is by changing your php script execution mode.
In Virtualmin>Server Configuration>Website Options there are a number of standard options. These are:
The first thing to do is try changing your php script execution mode to a different one from that which you have it currently set to.Quite likely, the default apache mod_php can be selected then, restart apache (can be done from the main Virtualmin dashboard)
then go back to your web broswer and try to access the url again.
Most often this is enough to get the problem Virtualmin Virtual Server website back online again.
Now, what if the php script execution mode that you absolutely must use is not working?
It may be that you want to use FCGId for example, and the browser throws an internal server error 500 when that mode is selected. One remedy is the check the apache2-suexec-custom module is installed and that your /etc/apache2/suexec/www-data file are correct. If your home directory in virtualmin file manager contains the appropriate directory (ie fcgi-bin), then your www-data file should contain the following lines:
Once you have ensured your file is correct, try restarting apache2 and browsing the webpage once more.