Answers
Writing a program so that it keeps working correctly whatever the user does and is easy to change.
How easy a program is to read, understand and update, by the original programmer or someone else.
Thinking ahead about how users might use a program in ways it was not intended.
Separate named sections of code that each do one job, so a change is only made once.
Allowing only a small number of tries before an account is locked and further entries are refused.
Confirming the identity of a user before letting them use the program or see its data.
The spaces at the start of lines inside a block that show which lines belong together.
Text shown on screen explaining why the value the user typed was not accepted.
Notes in a program that explain what a section of code does or why it was written.
Checking that data entered by a user is sensible and follows set rules before the program uses it.
Giving variables descriptive labels so that anyone reading the code can tell what each value is for.
Values that break the set rules for a field, which the program refuses and asks for again.
A secret word or phrase that is long and varied so it is hard to guess.