this is a nested lookup in pairs block
so what happens, if the webiste is not found?
the string “not found” will be returned
now the second lookup in pairs will be executed, however the string “not found” is not a list of lists, therefore that lookup in pairs block will get an error
and the suggestion will fix that like this
Now you might understand, how important it is to use Do it to debug your blocks, see also tip 4 here App Inventor: How to Learn | Pura Vida Apps
Taifun