Advanced Poll Cookie Problem

I installed Advanced Poll, and the poll works. However, I get this error message at the top of my page after voting. And it isn't caching cookies b/c when you hit refresh, it just keeps counting the same vote again and again. Can anyone help me out with this? I am pasting the error message below:

Warning: Cannot modify header information - headers already sent by (output started at /home/invigor/public_html/joyfultest.htm:3) in /home/invigor/public_html/poll/poll_cookie.php on line 21

If you want to go to the actual test page to see what it does go to: http://www.invigoratinginspiration.com/joyfultest.htm

Thanks!
Hope Wilbanks

Use the forums search function and look for Cannot modify header