On Error Resume Next

This statement allows execution to continue, effectively ignoring all run-time errors. This is not recommended.

The "Next" does not refer to the next line after this statement.
The "Next" refers to continuing the execution on the subsequent line, after the error has occurred.
This causes execution to continue with the statement immediately following the statement that caused the run-time error.
Be careful when using this statement because this will ignore run-time errors that could be unexpected.
Ignoring run-time errors will lead to logical-errors and unexpected behaviour.

This statement allows execution to continue when multiple run-time errors occur.

If you are anticipating a run-time error you can handle this by checking the Err Object.
When a run-time error occurs the Err object will contain details about the error.
You should always reset the Err object after the error has been handled.

Nested Subroutines

Unhandled run-time errors are passed up the call stack.
This "On Error Resume Next" error handling statement is still active inside the MySub2 subroutine.

Switching Off

You can turn this type of error handling off by using the "On Error GoTo 0" to switch back to the default type of error handling.