The internet was invented by scientists, not publishing experts, working under funding from DARPA (Defense Advanced Research Projects Administration), and believe me it shows! At the time the World Wide Web came into being, word processors were little more than jazzed-up text editors. The purpose of the Internet at that time was to organize and format scientific and engineering documents into standardized text-based files that a commonly used reader called a "browser" would render on any computer connected to ARPANET. Using "tags" similar to those incorporated by word processors of the time, they developed a standard called HTML, or, "Hyper Text Markup Language". ARPANET was later turned over to the private sector, when faster and more secure techonologies were adoptedc by the Department of Defense.
The first browser was Mosaic, developed by NCSA (National Center for Supercomputer Applications), a research institute at the University of Illinois. As the web became more open and publicly available, and cheaper technology made home computing possible, more browsers were developed and pandemonium reigned. Each browser had its own proprietary code buried inside it to determine how content was presented -- for example, what "bold", "strong" or "italic" text looked like. So, to put it mildly, web pages didn't look exactly alike on all browsers.
Soon it became apparent that specificity was required in the form of standards for document structure and HTML tag rendering. Many major software companies got together and formed the World Wide Web Consortium, or W3C, to develop a standard for interpreting (rendering on-screen) HTML. One of the early decisions was to force a separation of "content" and "presentation". Text and images are elements of content. Presentation is what the "content" looks like -- typeface (font), style (italic, bold, etc.), color, placement, size -- all these are now controlled by a separate language called CSS, or "cascading style sheets".
This course will adhere to the W3C standards for markup (modern XHTML -- "extended" HTML) and CSS (cascading style sheets). "Markup" is the system of invisible "tags" used to format the content (what appears between the tags), and CSS is what describes what the markup does.