3. The method according to claim 2 , wherein the switching is controlled in three stages including a first stage from a start of the obtaining operation of the page to a time of completion of acquisition of text data of the page, a second stage from the time of the completion of acquisition of the text data of the page to a time of completion of acquisition of the definition information, and a third stage after the completion of acquisition of the definition information, and wherein the onscreen representation in the text browsing mode is made during the first stage, notification notifying execution of the switching is added to the onscreen representation in the text browsing mode during the second stage, and the onscreen representation in which the definition information is applied is made during the third stage if the predetermined user operation is not performed.
3. The method according to claim 2 , wherein the switching is controlled in three stages including a first stage from a start of the obtaining operation of the page to a time of completion of acquisition of text data of the page, a second stage from the time of the completion of acquisition of the text data of the page to a time of completion of acquisition of the definition information, and a third stage after the completion of acquisition of the definition information, and wherein the onscreen representation in the text browsing mode is made during the first stage, notification notifying execution of the switching is added to the onscreen representation in the text browsing mode during the second stage, and the onscreen representation in which the definition information is applied is made during the third stage if the predetermined user operation is not performed. 4. The method according to claim 3 , wherein the operation for canceling the switching of the onscreen representation is allowed only in the second stage.