Mirror some folders between two ubuntu servers

[couper]

Hi
I have two server in different locations, they have internet connection.
Server A is the real server. Server B is for back-up.
I want to one-way mirror A to B some of the folder like var/www etc.
How can I do it?
Thanks

[vanadium]

rsync -av <source> <destination>

where both source and destination can also be remote locations, e.g.

rsync -av /home/user/data user@remoteserver.com:/home/user/

The remote computer must be accessible with ssh. rsync uses an ssh connection.

[couper]

is there any program uses http connection?
My remote server has 80 port open only.