Update: Sergio, the author of the livevalidation rails plugin updated the plugin so you can disregard the finale of the article (validates_confirmation_of is working, as well as the newest version of livevalidation, 1.3 is used in the plugin – so no additional tweaking is needed, install and validate away )
Surely I am not the only one who was a ‘bit nervous’ (that was a mild euphemism) when his carefully entered data disappeared after submitting a form to the server. Nowadays web applications are doing better than that – valid data is saved and only the problematic fields are pointed out.
Of course even that feels so 1990′s now. A contemporary (ehm… web 2.0?) web application is expected to validate the form on the client side already (WARNING! That doesn’t mean at all you shouldn’t validate on the server side though – client side validation is for the good guys but you should still look out for the script kiddies et al), pointing out the errors on the fly so there is no need to come back and change/edit those fields after submitting a form.
One more note: the Rails plugin contains version 1.2 but there is a newer version, 1.3 so be sure to replace it.