Binder is a free service to share and execute Jupyter notebooks. Some cloud providers and institutions are providing free resources to run the service. For more detail on Binder, please go to https://jupyter.org/binder.
Although Binder is very useful since anyone can run a notebook with zero setup, after some inactivity period the resources to execute your temporary Jupiter server will be reclaimed and the following page will show up upon a refresh:
This is why it's important to save your work from time to time because next time you start a new Binder through a link, the notebooks will revert to their original version.
First mode is using browser storage (easier to use), the second is using your laptop disk (less easy, but provide a usable copy of the notebook).
