From validator.w3.org/check

Line 5683 column 37: character "[" is not allowed in the value of attribute "name".

<form method="post" name="advanced[]" action="http://www.....

It is possible that you violated the naming convention for this attribute. For example, id and name attributes must begin with a letter, not a digit.

Are the old html arrays still valid in XHTML or do wee need to be using something different.

Ibbo

You'll nee new ones. XHTML is not HMTL, it follows XML rulings instead.

XHTML uses lists <ol> <ul> instead of arrays.

It was the brackets "[]" that make it fail. I have been told that html tags can replace them and still keep its functionality.

Yet to be tried and tested.

Thanks