This function verifies that the given user name and password matches one of the entries stored in the TCustomWebUserList object. Before the validation begins, it triggers the OnBeforeValidateUser event. If an error occurs during the validation check, the OnValidateUserError event will be triggered and a description of the error is sent, which could be either a missing or invalid password, or a missing or unknown user name. After the validation is complete, this function triggers the OnAfterValidateUser event.