checking websites other then the main domain

[hires]

Is there a possibility to check the websites of other domains within one and the same account? So when you type: http://www.maindomain.com/~accountname is can check the website of the main domain, but what if a customer has two or more domains within his own account, how can he check the websites for the other domains?

I tried visiting:
http://maindomain.com/~accountname/domains/otherdomain.com but the following error appears:

'Not Found
The requested URL
/~accountname/domains/otherdomain.com
was not found on this server.'

Thanks in advance.