1、Three Ways to Insert CSS

  • External style sheet
  • Internal style sheet
  • Inline style

External Style Sheet

With an external style sheet, you can change the look of an entire website by changing just one file!

Each page must include a reference to the external style sheet file inside the <link> element. The <link> element goes inside the <head> section:

<head>

<link rel="stylesheet" type="text/css" href="mystyle.css">

</head>

Internal Style Sheet

An internal style sheet may be used if one single page has a unique style.

Internal styles are defined within the <style> element, inside the <head> section of an HTML page:

<head>

<style>

body {

  background-color: linen;

}

h1 {

  color: maroon;

  margin-left: 40px;

}

</style>

</head>

Inline Styles

An inline style may be used to apply a unique style for a single element.

To use inline styles, add the style attribute to the relevant element. The style attribute can contain any CSS property.

The example below shows how to change the color and the left margin of a <h1> element:

<h1 style="color:blue;margin-left:30px;">This is a heading</h1>

2、CSS Colors

Colors are specified using predefined color names, or RGB, HEX, HSL, RGBA, HSLA values.

backgroud color 、 text color 、border color

Color Values

In HTML, colors can also be specified using RGB values, HEX values, HSL values, RGBA values, and HSLA values:

Same as color name "Tomato":

rgb(255, 99, 71)

#ff6347

hsl(9, 100%, 64%)

Same as color name "Tomato", but 50% transparent:

rgba(255, 99, 71, 0.5)

hsla(9, 100%, 64%, 0.5)

3、CSS Backgrounds

The CSS background properties are used to define the background effects for elements.

CSS background properties:

  • background-color
  • background-image
  • background-repeat
  • background-attachment
  • background-position

Background Image

The background-image property specifies an image to use as the background of an element.

By default, the image is repeated so it covers the entire element.

The background image for a page can be set like this:

body {

  background-image: url("paper.gif");

}

By default, the background-image property repeats an image both horizontally and vertically.

body {

  background-image: url("gradient_bg.png");

  background-repeat: repeat-x;

}

Background Image - Fixed position

To specify that the background image should be fixed (will not scroll with the rest of the page), use the background-attachment property:

body {

  background-image: url("img_tree.png");

  background-repeat: no-repeat;

  background-position: right top;

  background-attachment: fixed;

}

Background - Shorthand property

To shorten the code, it is also possible to specify all the background properties in one single property. This is called a shorthand property.

The shorthand property for background is background:

body {

  background: #ffffff url("img_tree.png") no-repeat right top;

}

4、CSS Borders

Border Style

The border-style property specifies what kind of border to display.

The following values are allowed:

  • dotted - Defines a dotted border
  • dashed - Defines a dashed border
  • solid - Defines a solid border
  • double - Defines a double border
  • groove - Defines a 3D grooved border. The effect depends on the border-color value
  • ridge - Defines a 3D ridged border. The effect depends on the border-color value
  • inset - Defines a 3D inset border. The effect depends on the border-color value
  • outset - Defines a 3D outset border. The effect depends on the border-color value
  • none - Defines no border
  • hidden - Defines a hidden border

The border-style property can have from one to four values (for the top border, right border, bottom border, and the left border).

Border Width

The border-width property specifies the width of the four borders.

The width can be set as a specific size (in px, pt, cm, em, etc) or by using one of the three pre-defined values: thin, medium, or thick.

The border-width property can have from one to four values (for the top border, right border, bottom border, and the left border).

Border - Shorthand Property

You can also specify all the individual border properties for just one side:

p {

  border-left: 6px solid red;

  background-color: lightgrey;

}

Rounded Borders

The border-radius property is used to add rounded borders to an element:

p {

  border: 2px solid red;

  border-radius: 5px;

}

5、CSS Margins

he CSS margin properties are used to create space around elements, outside of any defined borders.

With CSS, you have full control over the margins. There are properties for setting the margin for each side of an element (top, right, bottom, and left).

If the margin property has three values:

  • margin: 25px 50px 75px;

    • top margin is 25px
    • right and left margins are 50px
    • bottom margin is 75px
 

If the margin property has two values:

  • margin: 25px 50px;

    • top and bottom margins are 25px
    • right and left margins are 50px

The auto Value

You can set the margin property to auto to horizontally center the element within its container.

The element will then take up the specified width, and the remaining space will be split equally between the left and right margins:

div {

  width: 300px;

  margin: auto;

  border: 1px solid red;

}

The inherit Value

This example lets the left margin of the <p class="ex1"> element be inherited from the parent element (<div>):

<!DOCTYPE html>

<html>

<head>

<style>

div {

  border: 1px solid red;

  margin-left: 100px;

}

p.ex1 {

  margin-left: inherit;

}

</style>

</head>

<body>

<h2>Use of the inherit value</h2>

<p>Let the left margin be inherited from the parent element:</p>

<div>

<p class="ex1">This paragraph has an inherited left margin (from the div element).</p>

</div>

</body>

</html>

Margin Collapse

Top and bottom margins of elements are sometimes collapsed into a single margin that is equal to the largest of the two margins.

This does not happen on left and right margins! Only top and bottom margins!

Look at the following example:

<!DOCTYPE html>

<html>

<head>

<style>

h1 {

  margin: 0 0 50px 0;

}

h2 {

  margin: 20px 0 0 0;

}

</style>

</head>

<body>

<p>In this example the h1 element has a bottom margin of 50px and the h2 element has a top margin of 20px. Then, the vertical margin between h1 and h2 should have been 70px (50px + 20px). However, due to margin collapse, the actual margin ends up being 50px.</p>

<h1>Heading 1</h1>

<h2>Heading 2</h2>

All HTML elements can be considered as boxes. In CSS, the term "box model" is used when talking about design and layout.



The CSS box model is essentially a box that wraps around every HTML element. It consists of: margins, borders, padding, and the actual content.


</body>

</html>




similar padding


6、CSS Box Model


All HTML elements can be considered as boxes. In CSS, the term "box model" is used when talking about design and layout.


The CSS box model is essentially a box that wraps around every HTML element. It consists of: margins, borders, padding, and the actual content.








Explanation of the different parts:


  • Content - The content of the box, where text and images appear
    • 

  • Padding - Clears an area around the content. The padding is transparent
    • 

  • Border - A border that goes around the padding and content
    • 

  • Margin - Clears an area outside the border. The margin is transparent


7、CSS Outline


An outline is a line that is drawn around elements, OUTSIDE the borders, to make the element "stand out".


CSS has the following outline properties:


  • outline-style
    • 

  • outline-color
    • 

  • outline-width
    • 

  • outline-offset
    • 

  • outlin




Note: Outline differs from borders! Unlike border, the outline is drawn outside the element's border, and may overlap other content. Also, the outline is NOT a part of the element's dimensions; the element's total width and height is not affected by the width of the outline.




The outline-style property specifies the style of the outline, and can have one of the following values:


  • dotted - Defines a dotted outline
    • 

  • dashed - Defines a dashed outline
    • 

  • solid - Defines a solid outline
    • 

  • double - Defines a double outline
    • 

  • groove - Defines a 3D grooved outline
    • 

  • ridge - Defines a 3D ridged outline
    • 

  • inset - Defines a 3D inset outline
    • 

  • outset - Defines a 3D outset outline
    • 

  • none - Defines no outline
    • 

  • hidden - Defines a hidden outline


Outline - Shorthand property


The outline property is a shorthand property for setting the following individual outline properties:


  • outline-width
    • 

  • outline-style (required)
    • 

  • outline-color


The outline property is specified as one, two, or three values from the list above. The order of the values does not matter.




p.ex1 {outline: dashed;}

p.ex2 {outline: dotted red;}

p.ex3 {outline: 5px solid yellow;}

p.ex4 {outline: thick ridge pink;}




Outline Offset


The outline-offset property adds space between an outline and the edge/border of an element. The space between an element and its outline is transparent.


The following example specifies an outline 15px outside the border edge:




												


											
CSS：Tutorial one的更多相关文章
	

    
						
  1. CSS：Tutorial four
		
    1.CSS Tables To specify table borders in CSS, use the border property. The example below specifies a ...
    
		
    2. 
						
  2. CSS：Tutorial three
		
    1.CSS Links links can be styled differently depending on what state they are in. The four links stat ...
    
		
    3. 
						
  3. CSS：Tutorial two
		
    1.CSS Text text color, text align... Text Decoration The text-decoration property is used to set or  ...
    
		
    4. 
								
  4. Hover.css：一组超实用的 CSS3 悬停效果和动画
		
    Hover.css 是一套基于 CSS3 的鼠标悬停效果和动画,这些可以非常轻松的被应用到按钮.LOGO 以及图片等元素.所有这些效果都是只需要单一的标签,必要的时候使用 before 和 after ...
    
		
    5. 
						
  5. CSS：opacity 的取值范围是 0~1
		
    CSS:opacity 的取值范围是 0~1,难怪设置为 1~100 看不到效果.
    
		
    6. 
						
  6. CSS：CSS定位和浮动
		
    CSS2.1规定了3种定位方案 1.Normal flow:普通流(相对定位 position relative.静态定位 position static) 普通流(normal flow,国内有人翻 ...
    
		
    7. 
						
  7. CSS： word-wrap和word-break
		
    最近修改页面排版的一些问题,发现关于内容分词换行有两个主要的CSS: word-wrap 和 word-break 特别是word-wrap还有个取值break-word,更使得这两个属性容易混淆.  ...
    
		
    8. 
						
  8. CSS：不可思议的border属性
		
    原文:Magic of CSS border property 译文:不可思议的CSS border属性 译者:dwqs 在CSS中,其border属性有很多的规则.对于一些事物,例如三角形或者其它的 ...
    
		
    9. 
						
  9. Normalize.css：优化重置CSS默认属性
		
    Normalize.css:优化重置CSS默认属性 官方网站:http://necolas.github.io/normalize.css/ 项目仓库:https://github.com/necol ...
    
		
    10. 
		

	


随机推荐
	

    
									
  1. 003-mysql查询表的数据大小
			
    在需要备份数据库里面的数据时,我们需要知道数据库占用了多少磁盘大小,可以通过一些sql语句查询到整个数据库的容量,也可以单独查看表所占容量. 1.查看数据库表结构大小,要查询表所占的容量,就是把表的数 ...
    
			
    2. 
						
  2. redis的图形化工具(四)
			
    1. 介绍 本篇会介绍几个关于redis的图形化的监控工具和管理工具. 2. redis-stat redis-stat提供终端和web端的监控页面,它安装和使用起来很简单. 安装只需要一条指令. $ ...
    
			
    3. 
						
  3. Hive学习路线图--张丹老师
			
    前言 Hive是Hadoop家族中一款数据仓库产品,Hive最大的特点就是提供了类SQL的语法,封装了底层的MapReduce过程,让有SQL基础的业务人员,也可以直接利用Hadoop进行大数据的操作 ...
    
			
    4. 
						
  4. list comprehension & generator expression
			
    List comprehensions(列表推导式) are better when you want to iterate over something multiple times. Howeve ...
    
			
    5. 
						
  5. java反射基础知识（二）
			
    1. 了解 Java 中的反射 1.1 什么是 Java 的反射 Java 反射是可以让我们在运行时获取类的函数.属性.父类.接口等 Class 内部信息的机制.通过反射还可以让我们在运行期实例化对象 ...
    
			
    6. 
						
  6. go——数组（二）
			
    1.内部实现 在Go语言里,数组是一个长度固定的数据类型,用于存储一段具有相同的类型的元素的连续块. 数组存储的类型可以是内置类型,如整型或字符串,也可以是某种结构类型. 灰格子代表数组里面的元素,每 ...
    
			
    7. 
						
  7. Python（文件处理）
			
    二.基本操作 #r''------------------>> r:原生字符串,不判断符号的含义#文件处理 f=open(r’c:\a.txt’,’r’,encoding=’utf-8’) ...
    
			
    8. 
						
  8. GIL解释器，协程，gevent模块
			
    GIL解释器锁 在Cpython解释器中,同一个进程下开启的多线程,同一时刻只能有一个线程执行,无法利用多核优势 首先需要明确的一点是GIL并不是Python的特性,它是在实现Python解析器(CP ...
    
			
    9. 
						
  9. yii2查询数据倒序显示
			
    public function selectall(){ return $this->findBySql("SELECT * FROM article order by art_tim ...
    
			
    10. 
						
  10. PAT 天梯赛 L1-016. 查验身份证 【水】
			
    题目链接 https://www.patest.cn/contests/gplt/L1-016 AC代码 #include <iostream> #include <cstdio&g ...
    
			
    11.