1. A method that utilizes a processor to search for information about a search word provided by a user terminal in a system connected to a plurality of user terminals through a network, the method comprising: identifying search targets to be searched based on the search word that is provided by the user terminal through the network; performing a search process, using the processor, by applying different search criteria to the respective search targets; and providing search results for the respective search targets, wherein the search targets comprise at least one of the following: a unit configured to show a community on the network, an article configured to show contents posted in a community, and a sorting menu configured to indicate categories with different topics provided by a community, wherein the unit is searched based on a first search criteria that considers at least one of the following estimation factors: a community user reliability index, a community activity index, and a community volume, wherein the community user reliability index is indicative of a sum of reliability indexes of all users registered to corresponding communities, and each reliability index indicates a level of reliability of information the corresponding user provides, the community activity index is indicative of a level of activity with which the users registered to the corresponding community perform community activities, and is generated based on at least one of the following: number of contents posted within a predetermined time, number of users visiting the corresponding community, and number of other communities having predetermined relationships with the corresponding community, and the community volume is based on at least one of the following: number of users registered to the community and the number of contents posted in the community.