strange code at top of webpage

I tried to set up Overture Conversion tracking on the checkout success page by pasting the overture script into a file called jscript_overture.php and uploading it to inclues/modules/pages/checkout_success but on the checkout page I get some text at the very top of the page that says:

{\rtf1\ansi\ansicpg1252\deff0\deflang1033{\fonttbl{\f0\froman\fcharset0 Times New Roman;}{\f1\fswiss\fcharset0 Arial;}} {*\generator Msftedit 5.41.15.1507;}\viewkind4\uc1\pard\sb100\sa100\f0\fs24 \f1\fs20\par }

and everything else displays properly. The file I created starts with <SCRIPT LANGUAGE="JavaScript"> and ends with </SCRIPT>. Is there supposed to be something else in the file to make it a proper php file, or does anyone know why this might not be working properly.

That's the header of an RTF file. Use a plain text editor to modify your code, or make sure it is saved as plain text from the editor you are using.