Implementing Markup Validation Suggestions

I ran my site through the W3C Markup Validator to see if there were any errors and it suggested 13. The problem is that I can;t figure out how to correct the errors. For example, one error is described as so:

Error Line 10, Column 54: there is no attribute “prefix”
…://www.facebook.com/2008/fbml’ prefix=”og: http://ogp.me/ns#”&gt; <!–<![endif]–…

I can see the correct code by using HTML_tidy but how can I access this HTML on my own site to be able to change it? It’s probably very obvious, I ‘m just not up to scratch with this.

http://www.silverphotography.co.uk