Syntax: background-image : none | url (url)

Parameters: none: No background image (default) url: Use absolute or relative address to specify the background image

Syntax: background-repeat : repeat | no-repeat | repeat-x | repeat-y

grammar:

parameter:

grammar:

parameter:

1. Predefined color values, such as red, green, blue, etc.

.Hexadecimal, such as #FF0000, #FF6600, #29D794, etc. In practice, hexadecimal is the most commonly used way to define colors.

RGB code, such as red can be represented as rgb(255,0,0) or rgb(100%,0%,0%).

The ine-height attribute is used to set the line spacing, which is the distance between lines, that is, the vertical spacing of characters, generally called line height. There are three commonly used attribute value units for line-height, namely pixel px, relative value em and percentage %. The most commonly used unit in actual work is pixel px.

The text-align attribute is used to set the horizontal alignment of text content, which is equivalent to the align attribute in HTML.

The text-indent attribute is used to set the indent of the first line of text. Its attribute value can be a value in different units, a multiple of the em character width, or a percentage relative to the width of the browser window. Negative values ​​are allowed. It is recommended to use em as Set units.

The letter-spacing attribute is used to define word spacing, which is the space between characters. Its attribute values ​​can be values ​​in different units, negative values ​​are allowed, and the default is normal.

color: rgba(r,g,b,a) a means alpha, which means transparency. The value range is between 0 and 1. color: rgba(0,0,0,0.3)

Tag selector refers to using HTML tag name as selector

The class selector is identified by "." (English dot), followed by the class name

We can specify multiple class names for tags to achieve more choices.

The id selector is identified by "#", followed by the id name.

Use wildcard selectors to define CSS styles that clear the default margins for all HTML tags.

Pseudo-class selectors are used to add special effects to certain selectors. For example, add special effects to links. For example, you can select the 1st and nth elements.

:link /* Unvisited link */

:visited /* Visited links */

:hover /* Move the mouse to the link */

:active /* selected link */

A compound selector is composed of two or more basic selectors, combined in different ways, in order to select more accurate and detailed target element tags.

The intersection selector consists of two selectors, the first of which is the label selector and the second is the class selector. There cannot be a space between the two selectors.

The union selector (CSS selector grouping) is formed by connecting each selector with a comma. Any form of selector (including label selector, class selector, id selector, etc.) can be used as a union selector. part. If the styles defined by some selectors are exactly the same, or partially the same, you can use the union selector to define the same CSS style for them.

The descendant selector, also known as the inclusion selector, is used to select the descendants of an element or element group. It is written by writing the outer tag in front and the inner tag in the back, separated by spaces. When tags are nested, the inner tag becomes a descendant of the outer tag.

Child selectors can only select elements that are children of an element. The way to write it is to write the parent tag at the front, the child tag at the back, and connect it with a > in the middle. Note that there is a space left on the left and right sides of the symbol.

Selectors whose tags have certain special attributes are called attribute selectors.

E::first-letter The first word or character of the text (such as Chinese, Japanese, Korean, etc.)

E::first-line The first line of text;

E::selection can change the style of selected text;

<Tag name style="Attribute 1: Attribute value 1; Attribute 2: Attribute value 2; Attribute 3: Attribute value 3;"> Content </Tag name>

px: commonly used pixel unit

em: font size relative to the text within the current object

in: inches

cm: Centimeter

mm: millimeter

pt: point

The font-family property is used to set the font. Commonly used fonts in web pages include Song Dynasty, Microsoft YaHei, HeiTi, etc. For example, to set the font of all paragraphs of text in a web page to Microsoft YaHei, you can use the following CSS style code:

Usage: p{ font-family:"Microsoft Yahei";}

It is possible to set the font name in CSS and write Chinese directly. However, garbled errors will occur when the file encoding (GB2312, UTF-8, etc.) does not match. XP system does not support Chinese similar to Microsoft Yahei.

Option 1: You can use English instead. For example font-family:"Microsoft Yahei"

Option 2: Use Unicode encoding directly to write font names in CSS to avoid these errors. Use Unicode to write Chinese font names, and the browser can parse them correctly. font-family: "\5FAE\8F6F\96C5\9ED1" means setting the font to "Microsoft Yahei".

The font-weight attribute is used to define the thickness of the font. Its available attribute values ​​are: normal, bold, bolder, 100~900 (integer multiples of 100).

For example, italic: {font-style:italic}

The label tag defines the label (label) for the input element.

Function: Used to bind a form element. When the label is clicked, the bound form element will gain input focus.

How to bind elements?

The for attribute specifies which form element the label is bound to.

<select> <option>Option 1</option> <option>Option 2</option> <option>Option 3</option> ... </select>

A directory path created based on the location of the web page that references the file. Therefore, when web pages saved in different directories reference the same file, the paths used will be different, so it is called a relative path.

The image file and HTML file are in the same folder: just enter the name of the image file, such as <img src="logo.gif" />.

The image file is located in the lower-level folder of the HTML file: enter the folder name and file name, separated by "/", such as <img src="img/img01/logo.gif" />.

The image file is located in the lower-level folder of the HTML file: enter the folder name and file name, separated by "/", such as <img src="img/img01/logo.gif" />.

An absolute path is a directory path based on the root directory of the Web site. It is called absolute because it means that when all web pages reference the same file, the paths used are the same.

"D:\web\img\logo.gif", or the complete network address, such as "http://www.baidu.com/images/logo.gif".

The src attribute in this syntax is used to specify the path and file name of the image file. It is a required attribute of the img tag.

<tag name> content </tag name>

HTML tags:

Structural standards: Structure is used to organize and classify web page elements. We mainly learn HTML.

Performance standards: Performance is used to set the layout, color, size and other appearance styles of web page elements, mainly referring to CSS.

Behavioral standards: Behavior refers to the definition of web page models and the writing of interactions. We mainly learn Javascript.

1. Make the development prospects of the Web broader. 2. Content can be accessed by a wider range of devices. 3. Easier to be searched by search engines. 4. Reduce website traffic costs. 5. Make the website easier to maintain. 6. Improve page browsing speed.