You can edit your skin file to remove it. You can also remove the Register link. Removing the links from the skin file will removes those links from every page that uses the skin. If you have more than one skin file, you'll need to edit all of them.
But, you'll want to make sure that YOU can login as admin or host. This URLs should work, but you should test before editing the skin files:
http://mysite.com/login.aspx In the skin file, you'll want to remove [USER] and [LOGIN] from the html version of the skin, or remove
< dnn:USER runat="server" id="dnnUSER" / >
< dnn:LOGIN runat="server" id="dnnLOGIN" / >
from the ascx versions.