<p>Hello. My name is Inigo Montoya. You killed my father. Prepare to die. and <p>Hello. My name is Inigo Montoya. You killed my father. Prepare to die.</p> In contrast, XML is much more rigid: All XML documents must be well-formed, meaning that every begin tag needs to have a matching end tag: <president>Andrew Jackson</president> XML allows shortcuts Although XML requires any element to have a start and end tag pair, it does allow you to combine the two tags if the element is empty, meaning that no text is provided between the start and end tags. For example, the following two lines are equivalent. <device id=”3838-2020”></device> and <device id=”3838-2020”/> XML is case sensitive HTML is case insensitive, so long as you spell out the tag syntax correctly, the document is processed appropriately. Each of the following are valid HTML statements. <body bgcolor=”#FFFFFF”></body> <BODY BGCOLOR=”#FFFFFF”></BODY> <Body Bgcolor=”#FFFFFF”></Body> On the other hand, XML is case sensitive, so the following statements aren’t considered equal. <quote>Get used to disappointment.</quote> <QUOTE>Get used to disappointment.</QUOTE> To avoid confusion, you should consistently use either all lower- or upper- case characters for the XML, XSL, and XSLT documents that you create. However, I recommend consistently using lowercase characters because this is the convention that nearly everyone follows. 18 Part I:  Getting Started with XSLT