dns lookup by web browser is wrong

[lpd]

If hostname is "ubuntu" and http address is banana.ubuntu.com I get a normal message that the site does not exist.

If hostname is "ubuntu.mydomain.org" (my own domainname that is...) and http address is banana.ubuntu.com I see, using tcpdump that Firefox/Konqueror/Opera tries to reach banana.ubuntu.com.mydomain.org, this leads up to a message from my domain registrar that the domain I tried to reach is indeed registred with them (http://banana.ubuntu.com is visible in the browsers address field so you'd think that's where you are... but you're not... you're at banana.ubuntu.com.mydomain.org).

How to correct this? Is this even a bug?