You must modify Magento Base URL setting in the admin area to accomplish that. To do this, go to System > Configuration in your Magento admin area and select Web from the left menu. The URL that will be used for standard (HTTP) connections can be changed by selecting the Unsecure option and then editing the base URL field. Before investing in a Magento multi-store solution, avoid any potential drawbacks:  As the XML tree needs to be constructed for every site, take into account your server's resources. Applying dedicated servers with necessary specifications will make sense to satisfy the demand.  Don't forget about SEO, as duplicate material may become an issue.