registration page custom field question

[mic2100]

Hi,

I have made my own custom registration page to make it look less forum like, the problem i am having is when the user enters invalid data the page goes back to the registration page and i don't know how to get the values previously entered. i can see from the original registration page that the values are accessed using variables but what are the variables called. I was thinking of creating strict javascript to stop the page been processed with out the fields matching the required formats.

Thanks