How to enter a & character in input field

Hello all,
 
I have a form with several input and textarea fields. When I try to
enter a special character like &, <, > (xml markups), and submit the
form, I got a System error: -1072896749 and the system blocks.
How can I configure my input/textarea fields so that they accept such
characters.
Thanks in advance for any tips.
Regards,
 
Catherine