you can study xls language in the below link :
http://www.w3schools.com/xsl/xsl_languages.asp
CSS = Style Sheets for HTML
XSL = Style Sheets for XML
think the xml like html and xsl like css .
for example:
xml:
<?xml version="1.0" encoding="UTF-8" ?> <?xml-stylesheet href="hellostyle.xslt" type="text/xsl"?> <collection> <book> <author year= "1990" > John Doe </author> <title> JavaScript </title> <price> 10.99 </price> </book> <book> <author year= "2000" > Mary Jones </author> <title> Photoshop Secrets </title> <price> 15.99 </price> </book> <book> <author year= "2005" > Garry Po </author> <title> PHP Programming </title> <price> 20.99 </price> </book> </collection>