1. A method of controlling an operation of a mobile terminal, the method comprising: displaying contents on a webpage screen in response to a selection of an Internet access menu or contents on a file viewer screen in response to a selection of a file viewer menu; receiving at least one letter input from a user while the contents are displayed; retrieving an entry window including the received at least one letter; additionally receiving remaining letters input from the user through the entry window; and executing one of Access of Internet, Search through Internet Access and Search within a file based on a text input in the entry window, wherein the execution of one of the Search through Internet Access and the Search within a file is decided in response to a long key entry in which a numeric enter key is pressed for more than a predetermined time, and the execution of an other of the Search through Internet Access and the Search within a file is decided in response to a short key entry in which the numeric enter key is pressed for less than the predetermined time.