"Cannot generate system identifier" error while validating

Hi all, This isn't PHP related strictly - but my dynamic pages are causing my some W3C flavoured grief... I've been running a web page through the W3C MarkUp Validation Service and have nailed all the errors bar one (which just happens to occur 460 times!) - but I'm stumped to know how to get around it. When validating I get loads of: Line X, column Y: cannot generate system identifier for general entity "f" Line X, column Y: reference not terminated by REFC delimiter Line X, column Y: reference to external entity in attribute value The actual error comes from a hyperlink that passes a parameter on the Querystring, like this: 1. Line 58, column 62: cannot generate system identifier for general entity "f" ...ef="xt/xt_apollo_mark_read.php?i=all&f=1" class="ApolloBoldLink">Mark all boa ^ 2. Line 58, column 62: general entity "f" not defined and no default entity (explain...). ...ef="xt/xt_apollo_mark_read.php?i=all&f=1" class="ApolloBoldLink">Mark all boa I'm using XHTML 1.0 Transitional and iso-8859-1. The "explain" links don't explain a thing. Does anyone know what needs to be done in order to get a Querystring value like that through the validator? -- Best regards, Richard Davey http://www.phpcommunity.org/wiki/296.html