A method and system are provided which enhance a browser function in a portable terminal by controlling MIME types to be received and processed according to a network condition. User's preferred one or more MIME types can be previously set. When the portable terminal is connected to the server, it determines whether data transmission rate, use state and memory use state of the portable terminal are normal or abnormal. When the communication condition is abnormal, the portable terminal can control MIME types transmitted from the server. Although all the MIME types have been already received from the server, when the use state and memory use state of the portable terminal is abnormal, the portable terminal extracts the one or more MIME types set by a user and then releases memory resources that have been already allocated, thereby enhancing the browser performance.