[dipankar@localhost ~]$ su
Password: 
[root@localhost dipankar]# yum update
Loaded plugins: langpacks, refresh-packagekit
adobe-linux-x86_64                                       |  951 B     00:00     
Could not retrieve mirrorlist http://fedora.redhat.com/download/mirrors/fedora-core-20 error was
14: HTTP Error 503 - Service Unavailable
Error: Cannot find a valid baseurl for repo: core/20
[root@localhost dipankar]#