These pairs let you define rules for both conditions: an error condition and a "normal" (non-error) condition.
So you must check these values in order to protect your application.
You might also have certain restrictions on the values.
Even if users correctly enter an integer, for example, you might need to make sure that the value falls within a certain range. NOTE] Important Validating user input is also important for security.
In that case, the validation is performed as users work in the browser.
For example, suppose you specify that a value should be an integer.