I'm new here and new to XML and have a problem with displaying the data in an xml file.

I am using Expression Web to create a "Store" page using products listed in a XML file that I receive from an affiliate manager (CJ.com). They use a DOCTYPE statement in their XML file:
<!DOCTYPE product_catalog SYSTEM "http://www.cj.com/downloads/tech/dtd/product_catalog_1_1.dtd">

When I create the page I can see all the information listed for the products in Expression Web but when I open it in a browser I receive the default statement that no products were found. If I were to remove the DOCTYPE statement it works fine in the browser.

If it were just a static XML file I would remove the statement and move on but this file will be updated on a weekly basis and I don't want the hassle of editing it each week.

Sorry this is all vague but if someone could help me to understand the use of the DOCTYPE statement and the DTD file that it points to It would help greatly.