<p style ="padding-left: 35px;padding-top: 6px;"><%=link_to(t('mypage.live_order_btn'), {:action => "course_order",:id => course.id, :back_action =>params[:action]},:style=>"color:white;font-weight: bold;text-decoration: none;" )%></p>


text-decoration:none;是去下划线的代码