For the redirect you can do it one of two ways:
echo '<meta HTTP-EQUIV="REFRESH" content="0; url=http://www.yourdomain.com/thankyou.htm">';
or send it as an http header:
header("Location: http://www.yourdomain.com/thankyou.htm");
For the mysql error, your getting that because the table doesn't exist. Do you use a web-based administration panel for your mysql database such as phpmyadmin?
You need to create the tables to store the information in. Execute something like:
CREATE TABLE users (
id mediumint(9) NOT NULL auto_increment,
firstname varchar(255) NOT NULL,
lastname varchar(255) NOT NULL,
email varchar(255) NOT NULL,
telephone mediumint(11) NOT NULL,
city varchar(255) NOT NULL,
affiliation varchar(255) NOT NULL,
website varchar(255) NOT NULL,
questionSkillset mediumtext NOT NULL,
questionElements mediumtext NOT NULL,
questionDesign mediumtext NOT NULL,
date timestamp(14) NOT NULL,
PRIMARY KEY (id),
UNIQUE (EMAIL)
) TYPE=MyISAM;
Another thing you should think about is protecting against sql injection