I've build a contact form and it works, but I can't get the thankyou message to appear. I keep getting the following error message which I don't understand as I can see anything wrong with line 46. Any suggestions...I'm new!

Warning: Cannot modify header information - headers already sent by (output started at /home/content/24/10758824/html/contact.php:2) in /home/content/24/10758824/html/contact.php on line 46