Running Multiple Sites with WordPress
In the past, if you wanted to run several websites using the regular version of WordPress, you needed to install one copy for each site (there was a special version called WordPress MU which could handle multiple sites). With WordPress 3.0, that all changed: there's now just one version and you can administer many sites from a single installation. In multisite mode, a business owner can have a company site and a personal site, families can have a blog for each family member, a group can have a site for itself and each member, schools can have a separate site for each class — the possibilities are endless.
If you're trying to manage the content of two or more sites, it's a real time-saver to have to log in only once, but even if you're just the webmaster for a group of sites, imagine having to update or backup WordPress only once.
A new service called ManageWP.com was in beta at the time of this writing and it offers an interesting take on multiple WordPress sites. It provides a single interface from which you can manage sites hosted on different accounts or servers. If you already have a lot of sites, a service like this might be easier than trying to migrate them all to a single WordPress multisite installation.
ENABLING MULTISITE MODE
By default, WordPress is not installed with multisite mode on — it has to be activated. The process is ...