Why does my browser treat the XML Schema document at a URL as an XML document?

Hi Folks,

When I drag and drop an XML document (i.e., a file with the suffix .xml) into my browser, my browser recognizes it as an XML document and processes it accordingly. If the XML document has a stylesheet PI, then the browser styles the XML document using the stylesheet.

When I drag and drop an XML Schema document (i.e., a file with the suffix .xsd) into my browser, my browser informs me that it doesn't recognize the file type.

When I dereference this URL:

http://www.w3.org/2001/xml.xsd 

 (which appears to be a URL to an XML Schema document) my browser processes it like an XML document.

Why does my browser treat the XML Schema document at that URL as an XML document?

/Roger