By default, Internet Explorer actually does validate XML documents as it loads them, but you won't see any validation errors unless you check the parseError object.
Turning Validation On and Off
You can turn document validation on or off with the document object's validateOnParse property, which is set to true by default.
Here's an example; in this case, I'll load this XML document, error.xml. This document has a validation problem because the <NAME> element is declared to contain only a <FIRST_NAME> element, not a <LAST_NAME> element:
<?xml version = "1.0" standalone="yes"?> <!DOCTYPE DOCUMENT [ <!ELEMENT DOCUMENT (CUSTOMER)*> <!ELEMENT CUSTOMER (NAME,DATE,ORDERS)> <!ELEMENT NAME (FIRST_NAME)> ...