$(document).ready(function(){

    $('#a1').click(function() {
        $('#resize_area').css("font-size","1em");
        $('#resize_area_01').css("font-size","1em");
        $('#a_link_1').css("text-decoration","underline");
        $('#a_link_2').css("text-decoration","none");
        $('#a_link_3').css("text-decoration","none");
    })
    $('#a2').click(function() {
        $('#resize_area').css("font-size","1.3em");
        $('#resize_area_01').css("font-size","1.3em");
        $('#a_link_1').css("text-decoration","none");
        $('#a_link_2').css("text-decoration","underline");
        $('#a_link_3').css("text-decoration","none");
    })
    $('#a3').click(function() {
        $('#resize_area').css("font-size","1.7em");
        $('#resize_area_01').css("font-size","1.7em");
        $('#a_link_1').css("text-decoration","none");
        $('#a_link_2').css("text-decoration","none");
        $('#a_link_3').css("text-decoration","underline");
    })

});