My lessons are not displaying when I click on them. Only the text on the left side panel shows up. Nothing in the centre or right panel shows up. I am using Explorer.
Free Code Camp has been updated to use newer technologies. It makes the application much faster and it means that we can go much longer without having to do a huge migration like the recent one. However, Edge, Internet Explorer, and Safari are very bad about choosing not to adhere to standards and support new functionality in JS and CSS. Right now, that means that these browsers exhibit lots of unexpected behavior. If you become a web developer you will come to hate these browsers with every fiber of your being.
What can I do then to go on with the lessons?
Use Chrome or Firefox. (I recommend Chrome).
Thanks for your explanation.