Problems with subdomains

[qwerty]

Hi,

I've got this problem: when I create a subdomain Plesk doesn't give me any error and create de respective folders, but when I try to acess it by the browser he give me the error that i can't show me the web page. I don't understand what is happening.

I create the subdomains by admin way (I own the server). There is only one domain where the subdomains works fine (the core domain).

You can see the example: http://demo.lourisystems.com (doesn't work)
http://demos.digitalid.com.pt (works fine: core domain)

Should be a problem with some config file??? I don't understand much of Linux.

Will be greatful with somebody help.

Thanks in advance.

P.S.-Sorry my english...