newbie DNS question

I was wondering if there was a way to set up preferences for web sites in
DNS much like you set preferences for mail servers. Say I have a site
running simultaneously on a Dell poweredge and a backup of it running on a
Compaq proliant. I always want to use the dell to host the site, but if the
Dell goes down I want DNS to recognize this and begin using the Compaq to
serve the site with the backup. Is it possible to do this in DNS, or is
there another way to do this. Maybe with virtual domains in Apache. Thanks
in advance for help on a newbie question.

- Joel