Hi,
one question:
Do the users select their birthday and the country they live in with these selects ?
At least in case of the birthday (if birthday at all):
Did you already think about using standard text inputs for the values of year, month and day. In the script that receives the data you could then use one of the php functions to check if the submitted birthdate is valid at all. This might be easier than doing it with selects.
Thomas