This is the fallback domain for services hosted under strugee.net. It exists to give a useful error message when no other reasonable action can be taken.
If you visited null.strugee.net directly, this was served to you as a regular webpage. All is well.
If you are unable to load any domain under strugee.net (including strugee.net itself) because you were redirected here, then the Apache webserver serving your request was unable to determine which domain you were requesting resources from.
The most likely reason for this is that you are running Internet Explorer version 6 or below. If this is the case, then please for the love of God upgrade your web browser (or even better, switch to Firefox). If this is not the case, please ensure that your browser is sending the Host: HTTP header. It may be that an extension is interfering with this functionality.
You may have requested a webpage for a service that does not run over HTTP. For example, imap.strugee.net is designed to be used with IMAP, not HTTP, and thus does not serve HTTP requests.
You may have requested a webpage for a service that uses HTTP, but has not been set up yet. This condition occurs when the administrator has set up a DNS record to reserve the name for future use, but has not set up the application that is to run on that subdomain.