css style sheet refers to Cascading Style Sheets (CSS), a computer language used to express file styles such as HTML or XML, and a programming language used to express HTML styles. Language is a style language that can separate web pages and content.
The operating environment of this tutorial: Windows 7 system, CSS3 version, Dell G3 computer.
css style sheet generally refers to CSS (cascading style sheet).
Cascading Style Sheets (English full name: Cascading Style Sheets) are files used to express HTML (an application of Standard Generalized Markup Language) or XML (a subset of Standard Generalized Markup Language). The computer language of styles is a programming language used to express HTML styles. It is a style language that can separate web pages and content.
CSS is mainly used to design the style of web pages and beautify web pages; it can not only statically modify web pages, but also dynamically format various elements of web pages in conjunction with various scripting languages.
CSS can perform pixel-level precise control over the layout of element positions in web pages, supports almost all font size styles, and has the ability to edit web page objects and model styles.
Composition of css
css definition consists of three parts: selector, attribute, attribute value
选择符{属性:属性值;}
1. Selector: also known as Selectors, all tags in HTML language are controlled through different css selectors.
2. Attributes: mainly include font attributes, text attributes, background attributes, layout attributes, border attributes, list item attributes, table attributes, etc. Some of these attributes are only supported by some browsers, which makes the use of CSS attributes more complicated
3. Attribute value: is the valid value of a certain attribute. Attributes and attribute values are separated by ":" semicolons. When there are multiple attributes, use ";" to separate them.
Note: h2 is the selector; font-family is the attribute; "宋体" is the attribute value
css selector
Commonly used ones include tag selector, category selector, id selector, etc.
1) Tag selector (also called element selector, type selector)
what: HTML page is composed of many tags, such as image tag , hyperlink tag , table tag
, etc. The css tag selector declares which tags on the page adopt css styles.
Example:
<style>
a{
font-size:9px;
color:#F93;
}
<style>
2) Category selector
Format: Dot (.) Category name
There are limitations to using tag selectors. If you declare a tag selector, all content of that tag in the page will change. Suppose there are 3
tags on the page. If you want each
to display differently, you can use the category tagger.
The HTML tag of the category selector only needs to be declared using the class attribute.
In HTML tags, you can apply multiple category selectors, which allows HTML to load the styles of multiple category selectors at the same time. Use spaces to separate multiple category selectors, for example:
.
3) id selector
The id selector selects and adds styles through the id attribute in the HTML page, which is basically the same as the category selector.
Format: "#" id attribute value
The named id selector should start with "#", followed by the "#" in the HTML tag id attribute value.
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