标签导航：标签由 组成
，我们使用元素来标记当前页面。固定导航标签样式的位置，位置：固定；属性被使用。
句法：
content....
. . .
例子：
GeeksforGeeks
HTML Introduction
HTML stands for Hyper Text Markup Language.
It is used to design web pages using markup
language. HTML is the combination of Hypertext
and Markup language. Hypertext defines the link
between the web pages. Markup language is used
to define the text document within tag which
defines the structure of web pages. This language
is used to annotate (make notes for the computer)
text so that a machine can understand it and
manipulate text accordingly. Most of markup
(e.g. HTML) languages are human readable.
Language uses tags to define what manipulation
has to be done on the text.
GeeksforGeeks
CSS Introduction
Cascading Style Sheets, fondly referred to as CSS,
is a simply designed language intended to simplify
the process of making web pages presentable. CSS
allows you to apply styles to web pages. More
importantly, CSS enables you to do this independent
of the HTML that makes up each web page. CSS is easy
to learn and understood but it provides powerful
control over the presentation of an HTML document.
GeeksforGeeks
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