class_ = if want to use class(reserved key) as an attribute(variable) need to use class_(underscore) flask: ===== clear cache on the web browser & show updated changes on the browser: shift + refresh button 2.If we want to edit any website template oneline on any web browser: right click > inspect > console >cmd: document.body.contentEditable=true + Enter Then we can edit anything online & want see the same changes from next time need to: right click > save the file > replace the index.html with changed filename.html