tooltips in registration form

Hey guys,

you seem to have implemented some beautiful "error"-tooltips in the registration form since v.1.3.x - really like it!

just have 2 small questions that might be interesting for other users as well:
- is there a simple way to change the error message without hacking the core? (I tried joomla language override but it didnt seem to work?)

- how can I use the tooltips for helping messages: like a user activating the input field and a green tooltip saying "please enter youre xxyyzz".

thanks in advance