Validation error messages represent the main way of signalling that an invalid value has been used in an input component. When an end-user enters an invalid value, an error message appears in a tooltip when the mouse hovers over an error icon displayed next to the input component.
There are two types of error messages: default and custom. Custom error messages are defined for specific criteria and override the default error message. When no custom error message is defined for a criterion, the default is used.