The FP field validation should come up with alert boxes like you want, but
it might depend on the validation methods eg does your form only need
"required" fields, or more complex such as a field must have a min and max
number of characters, or numbers only etc?
Otherwise, you will have to write your own, or search for a "validation"
script (eg
http://javascript.internet.com is a good resource for these types
of things)....the FP validation is a basic way of doing form field
validation without much in the way of options to configure it.
I think the way you describe it behaving is because it tests all the
validation/values "on submit" not as you proceed through each field, so it
presents the list of wrong things at the end, rather than alerting you to
wrong input as you go.