Advanced Poll error

HI guys, being a newbie to web design etc i need some help on the Poll script. I have manged to install it ok and it shows up fine on the website. However when you place a vote, the page refreshes and shows the number of votes etc but also shows this error message at the top.

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

This doesnt appear to have any effect on the poll as the data seems to be collecting ok, just need to get rid of this message!

Any ideas?

Thanks in anticipation

Aswhat happens with a lot of these logs, i managed to find the solution.
the first PHP text was not put on line 1 of my index page, although it was above the html tag. Moving it to the top line sorted this error out.