I dont know why did it show error in one aspx page while not in another , but anyway I did below solution :
Solution : You have to remove Title property of masterpage reference string(very first line of .aspx page) in the aspx page you are having error.
Before :
<%@ Page Title="" Language="vb" AutoEventWireup="false" MasterPageFile="~/masterpg0.Master" CodeBehind="course_details.aspx.vb" Inherits="education.course_details" %>
After :
<%@ Page Language="vb" AutoEventWireup="false" MasterPageFile="~/masterpg0.Master" CodeBehind="course_details.aspx.vb" Inherits="education.course_details" %>