4. A computer-implemented method for suggesting at least one recommended keyword in a network search, using a computer processor in communication with a computer network and a related search word database that stores related search words associated with a certain keyword in a plurality of computer servers in the computer network, the method comprising executing the following steps by a computer: displaying a first set of search results associated with a certain keyword input by a user at a website, each of the search results listing a site on the network directly accessible on the network by the user when the each of the search results is selected by the user; extracting at least one keyword associated with the certain keyword from the related search word database in a database storage device; providing at least one display score for the at least one extracted keyword, each of the at least one display score being associated with an expected revenue from advertisement of each of the at least one extracted keyword on a website; and determining at least one recommended keyword from among the at least one extracted keyword to be displayed on a website in addition to the first set of search results, based on the provided at least one display score; wherein the at least one recommended keyword enables display of a second set of search results related to one of the at least one recommended keyword when the one of the recommended keyword is selected by the user; and wherein the providing of the at least one display score comprises: providing a Pay Per Click (PPC) value of each of the at least one extracted keyword, and a Click Through Ratio (CTR) of an advertisement region of a website where advertisements corresponding to the at least one extracted keyword are displayed; and calculating the at least one display score of each of the at least one extracted keyword, based on the PPC value and the CTR, wherein the at least one display score is calculated further based on a display frequency of the at least one extracted keyword for denoting a weight according to the display frequency, and the weight based on a number of times that the at least one recommended keyword has been actually selected by the user is assigned to the at least one display score.
4. A computer-implemented method for suggesting at least one recommended keyword in a network search, using a computer processor in communication with a computer network and a related search word database that stores related search words associated with a certain keyword in a plurality of computer servers in the computer network, the method comprising executing the following steps by a computer: displaying a first set of search results associated with a certain keyword input by a user at a website, each of the search results listing a site on the network directly accessible on the network by the user when the each of the search results is selected by the user; extracting at least one keyword associated with the certain keyword from the related search word database in a database storage device; providing at least one display score for the at least one extracted keyword, each of the at least one display score being associated with an expected revenue from advertisement of each of the at least one extracted keyword on a website; and determining at least one recommended keyword from among the at least one extracted keyword to be displayed on a website in addition to the first set of search results, based on the provided at least one display score; wherein the at least one recommended keyword enables display of a second set of search results related to one of the at least one recommended keyword when the one of the recommended keyword is selected by the user; and wherein the providing of the at least one display score comprises: providing a Pay Per Click (PPC) value of each of the at least one extracted keyword, and a Click Through Ratio (CTR) of an advertisement region of a website where advertisements corresponding to the at least one extracted keyword are displayed; and calculating the at least one display score of each of the at least one extracted keyword, based on the PPC value and the CTR, wherein the at least one display score is calculated further based on a display frequency of the at least one extracted keyword for denoting a weight according to the display frequency, and the weight based on a number of times that the at least one recommended keyword has been actually selected by the user is assigned to the at least one display score. 6. The method of claim 4 , wherein the at least one recommended keyword is determined at every unit period, based on the at least one display score provided at the every unit period, and the at least one recommended keyword determined to be displayed during a current unit period is provided to users who entered the certain keyword during the current unit period.