ptg16476052What HTML Is (And What It Isn’t) 433
HTML defines a set of common elements for web pages: headings, paragraphs, lists, and
tables. It also defines character formats such as boldface and code examples. These ele-
ments and formats are indicated inside HTML documents using tags. Each tag has a spe-
cific name and is set off from the content of the document using a notation that I discuss
a bit later.
HTML Does Not Describe Page Layout
When you’re working with a word processor or page layout program, styles are not just
named elements of a page; they also include formatting information such as the font size
and style, indentation, underlining, and so on. So, when you write some text that’s sup-
posed to be a heading, you can apply the Heading style to it, and the program automati-
cally formats that paragraph for you in the correct style.
HTML doesn’t go this far. For the most part, the HTML specification doesn’t say any-
thing about how a page looks when it’s viewed. HTML tags just indicate that an element
is a heading or a list; they say nothing about how that heading or list is to be formatted.
The only thing you have to worry about is marking which section is supposed to be a
heading, not how that heading should look.
Although HTML doesn’t say much about how a page looks when
it’s viewed, Cascading Style Sheets (CSS) enable you to apply
advanced formatting to HTML tags. HTML has evolved to the
point where web publishers are intended to use CSS for format-
ting instructions. You’ll learn about CSS later in the book.NOTEWeb browsers, in addition to providing the networking functions to retrieve pages from
the Web, double as HTML formatters. When you read an HTML page into a browser
such as Firefox, Chrome, or Internet Explorer, the browser interprets, or parses, the
HTML tags and formats the text and images on the screen. The browser has mappings
between the names of page elements and actual styles on the screen; for example, head-
ings might appear in a larger font than the text on the rest of the page. The browser also
wraps all the text so that it fits into the current width of the window.
Different browsers running on diverse platforms style elements differently. For the most
part, browsers have standardized on the styles associated with the various HTML tags,
but there are some cases where they differ. Some non-smartphones display web pages
very differently than desktop and smartphone browsers; for example, they might not pro-
vide support for multiple fonts or even italics on a web page. More importantly, browsers