When a web browser displays a page such as the one you are reading now, it reads from a plain text file, and looks for special codes or “tags” that are marked by the < and > signs. The general format for a HTML tag is:
<tag_name>string of text</tag_name>
As an example, the title for this section uses a header tag:
<h3>What are HTML tags?</h3>
This tag tells a web browser to display the text What are HTML tags? in the style of header level 3 (We’ll learn more about these tags later). HTML tags may tell a web browser to bold the text, italicize it, make it into a header, or make it be a hypertext link to another web page. It is important to note that the ending tag,
contains the “/” slash character. This “/” slash tells a web browser to stop tagging the text. Many HTML tags are paired this way. If you forget the slash, a web browser will continue the tag for the rest of the text in your document, producing undesirable results (as an experiment you may want to try this later).
NOTE: A web browser does not care if you use upper or lower case. For example, <h3>...</h3> is no different from <H3>...</H3>
Unlike computer programming, if you make a typographical error in HTML you will not get a “bomb” or “crash” the system; your web page will simply look, well… wrong. It is quick and easy to go inside the HTML and make the changes.
Your browser has a small but open vocabulary! An interesting aspect of HTML is that if the browser does not know what to do with a given tag, it will ignore it! For example, in this document you are viewing, the header tag for this section really looks like this:
<wiggle><h3>What are HTML tags?</h3></wiggle>
but since your browser probably does not support a <wiggle> tag (I made it up, perhaps in the future it could cause the text to wave across the screen?), it proceeds with what it knows how to do. If I were programming a new web browser, I might decide to add the functionality for the <wiggle> tag into my software.