Validator Error message. Link gives 404

Dear Mailing List,

I have validated one of my pages and got an error about Non SGML character numbers.
See http://validator.w3.org/check?uri=http%3A%2F%2Ftest2.uc4.co.uk%2Fsightvillage%2F6-3-SVexhibitor-details.asp%3FID%3D181

The two links to Alan Flavell's articles are returning 404 errors.

Kind Regards

Ben Lomax