ABSTRACT
HTML is the standard way to represent documents for presentation in web browsers, and CSS is the standard way to describe how it should look. Both are more complicated than they should have been, but in order to create web applications, we need to understand a little of both. An HTML document contains elements and text. Elements are shown using tags: an opening tag <tagname> shows where the element begins, and a corresponding closing tag </tagname> shows where it ends. The text in an HTML page is normal printable text. However, since < and > are used to show where tags start and end, we must use escape sequences to represent them, just as we use \” to represented a literal double-quote character inside a doublequoted string in JavaScript. Headings and paragraphs are all very well, but data scientists need more.
