domainmapping

Hello, i have made a subdomain and changed the a records on another server, so far so good. But when I want to ‘map’ and enter the domainname of the blog in the subdomain, the domainname simply dissappeares .

Also when I browse to the new domainname, it shows the signup page and not the mapped domain. Has this somethiong to do with shared hosting?

Thanks

Frenk