Semantic — to show, to explain by sign or language.   The language of the World Wide Web is HTML, HyperText Markup Language.   All Web pages are written with HTML.

The key to HTML is in the tags, keywords enclosed in less than (<) and greater than (>) signs, that indicate what kind of content is coming.

This content includes but is not limited to, simply paragraphs such as this one, lists, images and links to other “web pages”.

HTML provides to the viewer the content, the structure, of the web page.   The format of a web page, while not necessary, is most often controlled by CSS, Cascading Style Sheets.   The study of CSS is probably more extensive than is the study in HTML.   Prior to the development and use of CSS, formatting a HTML page was handled completely within the HTML coding.   Many of the attributes used in early HTML are no longer acceptable.   However, once CSS is mastered or understood to a large extent, its use reduces greatly the volume of HTML used.   Suddenly, reading the HTML becomes easier for the designer and continuity between all pages within the web site is vastly easier to manage.

Sidebars are used to create one or more narrow columns on one side or both of the center of the page.   Frequently, inside these sidebars are navigation menus to other related pages and/or advertisements.

The sidebar is created through the use of a block element such as a “div” that is floated by the employment of CSS.   There must be a width specified unless the sidebar contains an image.   Flexible widths both in the sidebar and center content can be facilitated by specifying the width as a percent, the percentage of the total viewer's view port.