HTML and CSS Reference
In-Depth Information
HTML defines a set of common styles for web pages: headings, paragraphs, lists, and
tables. It also defines character styles such as boldface and code examples. These styles
are indicated inside HTML documents using tags . Each tag has a specific 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 work 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 supposed
to be a heading, you can apply the Heading style to it, and the program automatically
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.
So, as with the magazine example and the layout person who formats your article, the
layout person's job is to decide how big the heading should be and what font it should be
in. The only thing you have to worry about is marking which section is supposed to be a
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 formatting
instructions. I'll talk about CSS later in this lesson.
Web 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, Safari, 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, headings might
be 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 might style elements differently. Some
browsers might use different font styles than others. For example, a browser on a desktop
computer might display italics as italics, whereas a handheld device or mobile phone
might use reverse text or underlining on systems that don't have italic fonts. Or it might
put a heading in all capital letters instead of a larger font.
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