I have a HTML service with many pages on my disk. When I click index.htm in root folder all works fine - I can browse it without problem. Now I created some other flask program with navigation bar. In this navigation bar I have one bookmark where I'd like to open mentioned HTML service, to let me navigate this HTML service with Flask navigation bar on top. At the moment I added {{%extend "base.html"%}} and {{%block content%}} at the beginning and {%block end%}} at the end of all index.htm files of this HTML service. Main index.htm located in templates opens fine but clicking on any link guiding to 404 error. My route for this bookmark looks like: @app.route("/first") def view_Intranet_page(): return render_template("index.htm", title="Intranet page") Folders and files location looks like: d:\\main_folder |-templates |- index.htm | |- folder_for_link_1 | |- index.htm | - all flask files Index in templates works fine it is called by above route - it shows link 127.0.0.1:5000/first Index.htm in "folder_for_link_1" generates 404 error - it shows link 127.0.0.1:5000/folder_to_link_1/index.htm How to force this Flask app to let me browse all HTML service? Continue reading...