Why can't I delete a file even though I have write permissions?

The shell session should say everything: I can't delete a file (movie.avi) although I have write permissions. I don't get what the problem is. Have I missed something?

confus@homeserver:/home/narur$ id
uid=1000(confus) gid=1000(confus) groups=1000(confus),4(adm),24(cdrom),27(sudo),30(dip),46(plugdev),106(lpadmin),117(sambashare),118(debian-transmission),1001(narur)

confus@homeserver:/home/narur$ ll | grep movie.avi 
-rw-rw----  1 narur narur 1,4G Jan 11 09:42 movie.avi

confus@homeserver:/home/narur$ rm movie.avi 
rm: cannot remove `movie.avi': Permission denied

# # # # SOME INFOS ON MY SYSTEM:
confus@homeserver:/home/narur$ lsb_release -dc
Description:    Ubuntu 12.10
Codename:   quantal
confus@homeserver:/home/narur$ uname -a
Linux conserve 3.5.0-21-generic #32-Ubuntu SMP Tue Dec 11 18:51:59 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux

To delete a file you don't need write permission for the file but write and execute permissions for the folder the file is in.