Under our organiztion's Change Management policy, we require that certain actions occur before other actions (e.g. the change request must be fully approved before any implementation can occur). We have date fields on the change request form that we use to check these actions.
When users accidently has a typo in the date field that would make the dates go against of policy, we would like to have 'warning message' functionality that would act like a validation rule, but instead of preventing a save, it would just present a pop-up window with custom text where we could alert users to the possibility of that typo. They could click 'OK' to the pop-up message and then the save still occurs and they could choose to change the value after the save.
Maybe the best way to implement this is to add a feature to validation rules that turns the validation into a 'warning message' instead of a preventative function.