How can I install a web application to document root?

[Ville Talus]

I'm having a little bit of a problem when installing a web application to the document root. When creating a domain, is there some setting that enables or disables the document root option?

I'm asking this because for some times the document root option is disabled, I can't choose it. I haven't found a way to enable it. I've tried to change settings but still it doesn't work. I've also tried to read admin and reseller guide but seems to be nothing there.

Please can somebody help me?