Assuming you may have just cut and pasted it into a new page, or brought the old page over, are you sure your directory structure is the same. See "red" below.
Also if you're taking a backup and installing it on another site, are you sure that there is the same names and permissions set?
To the above css statement in the poll.php page, I've even added a background image to the poll. I am sure I could do a color changed to. I have about 30+ polls running on my site and up until now, they've all had the same black background, but now I can make it do anything.
See the red code above and ad this line under the td line
<?php
/* Include this before your html code */
include_once "poll/poll_cookie.php";
?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Untitled Document</title>
<style type="text/css">
<!--
td{ text-align:left}