not sure what/why...

[shantenujha]

In http://radical-cybertools.github.io/entk/try_it_online.html

for 2. 3, 2.4 and 2.5 "Please execute previous Shells"

[iparask]

There has to be an event sequence. This message is provided if a user presses an "Execute" button without pressing the previous ones that are needed.

If you think we can convey this message differently, I am happy to change it everywhere.

[vivek-bala]

Agree with Giannis. Although if you think "Please execute previous Shells" is not informative, we can discuss.