Comment 22 for bug 232469

This could be useful for suggestion #2, gnome-network-properties while applying system proxies could use /etc/profile.d/

Creating the following files in /etc/profile.d, and then this will work in *any* shell for *any* user of the system

#proxy.sh
export http_proxy=http://host.com:port/
export ftp_proxy=http://host.com:port/
export no_proxy=.domain.com
export HTTP_PROXY=http://host.com:port/
export FTP_PROXY=http://host.com:port/

#proxy.csh
setenv http_proxy http://host.com:port/
setenv ftp_proxy http://host.com:port/
setenv no_proxy .domain.com
setenv HTTP_PROXY http://host.com:port/
setenv FTP_PROXY http://host.com:port/

Source: www.fedoraforum.org/forum/printthread.php?t=742