Digression: HTML

• The structure of a HTML document (or Web page) is described using embedded formatting codes (or tags) intermingled with the information in the document.
   
  
• The HTML, the markup tags are delimited by the special characters "<" and ">". If either of these characters must appear as part of the actual data, they are written as < and > respectively.
   
  
• Philosophical note: it has been regarded as a mistake to use HTML to strongly enforce a particular layout (or appearance) of a document. One of the fundamental ideas of the Web is that the document creator cannot control how the browser will display it. Furthermore, defining only the document's structure allows us to extract information in a way which would otherwise be quite difficult. See also CSS, later.
   
  
• A HTML document is (despite sometimes looking rather formidable) lines of plain ASCII text.