I have an RSS feed generated by PHP. I have <?xml version="1.0" encoding="iso-8859-1"?> <rss version="2.0"> <channel> <title>TackyPenguin.com RSS feed</title> <description>Get all of the latest blogs from TackyPenguin.com</description> <link>http://tackypenguin.com</link> Code (markup): at the top of it. Feed burner says: The URL you entered does not appear to be a valid feed. We encountered the following problem: Error on line 2: The processing instruction target matching "[xX][mM][lL]" is not allowed. Code (markup): Can somebody tell me what the problem is?