Web-based Distributed Authoring and Versioning, or WebDAV, is a set of extensions to the Hypertext Transfer Protocol (HTTP) which allows users to collaboratively edit and manage files on remote World Wide Web servers.
Tutorial - http://www.ibiblio.org/pub/Linux/docs/HOWTO/other-formats/html_single/Apache-WebDAV-LDAP-HOWTO.html#AEN228
Apache needs to be configured and compiled with the --enable-dav option.
Uncomment the WebDAV config file in /usr/local/apache2/conf/httpd.conf:
# Include conf/extra/httpd-dav.conf