Confused at error message

We get this when we validate our page, but we dont understand what this
means or how to fix it. Can you help?

Target: http://www.alliance-leicester.co.uk/home/terms.asp
Please, validate your XML document first!

Line 2

Column 6

The processing instruction target matching "[xX][mM][lL]" is not allowed.



PS. The page passed W3C XHTML validation without problems

Alexa McMinn
Senior Website Content Editor
Alliance & Leicester