You can create a subdirectory _data at the same folder as html file.
Download the attached gif and put it there if you want to use the previous download version.
I have update that applet to EJS version 4. It should work fine if you download again.
You can double click downloaded ejs_tigerNmirror.jar and it should run.
(EJS version 4 is different from EJS 3, and the distribution files are also different--- jar instead of ZIP).
You can generate animated gif from the simulation when running EJS4 applications.
You will find many new options available if you [b]Right Click[/b] in the simulation region when you run the jar file locally.