See w3school/html
1. HTML element syntax
Note: end tags cannot be omitted in future HTML versions. W3school uses lower-case tags because the W3C is in HTML 4.Recommendation
Use lower-case letters, and in future (x) HTML versionsForce
Use lower-case letters.
2. html attributes
HTML tags can haveAttribute
. Attribute provides HTML elementsMore information
.
Attributes always appear in the form of name/value pairs, such:Name = "value"
.
Attribute is always in the HTML ElementStart tag
.
Note: attributes and attribute values are case sensitive.Insensitive
. However, the World Wide Web Alliance recommends lower-case attributes/attribute values in its HTML 4 Recommendation Standard. XHTML requires lower-case attributes/attribute values.
Attribute values should always be enclosed in quotation marks. Double quotation marks are the most commonly used, but it is no problem to use single quotation marks.
.
HTML 4.01/XHTML 1.0 Reference Manual
3. html title
By default, HTML automatically adds an extra blank line before and after block-level elements.
For example, before and after a paragraph or title element.
Make sure that the HTML heading label is used only for the title. Do not use titles only to generate bold or large text.
The search engine uses the title to index the structure and content of your web page.
H1 should be used as the title (the most important, Seo practices)
, Followed by H2, followed by H3, and so on.
4. html Section
Tip: it is a bad habit to insert an empty row with an empty section mark <p> </P>. Replace it with the <br/> label!
When the page is displayed, the browser will removeSource code
Extra spaces and empty rows. All consecutive spaces or empty rows are counted as one space.
.
5. html Text Formatting example
<PRE> <br/> This is <br/> pre-formatted text. <Br/> it retains spaces <br/> and line breaks. <Br/> </PRE> <br/> <p> pre labels are suitable for displaying computer code: </P> <br/> <PRE> <br/> for I = 1 to 10 <br/> print I <br/> next I <br/> </PRE>
6. html Style
The role of the style attribute:
Provides a common method to change the style of all HTML elements.
Style is introduced in HTML 4, which is a new preferred way to change the style of HTML elements. HTML styles can be directly added to HTML elements by using the style attribute, or indirectly defined in an independent style table (CSS file.
In HTML 4, tags and attributes are discarded.
. Deprecated means that tags and attributes will not be supported in future HTML and XHTML versions.
Tag |
Description |
<Center> |
Defines the center content. |
<Font> and <basefont> |
Define the HTML font. |
<S> and <strike> |
Define strikethrough text |
<U> |
Define underline text |
Attribute |
Description |
Align |
Define text alignment |
Bgcolor |
Define background color |
Color |
Define text color |
For these labels and attributes, use style instead!
7. HTML link
You can use the target attribute to define where the linked document is displayed.
The name attribute is used to create bookmarks in HTML. Bookmarks are not displayed in any special way and are invisible to readers. When named anchors is used, you can create a link directly to a section on the page, so that users do not need to scroll the page to find the information they need.
8. HTML list
You can use paragraphs, linefeeds, images, links, and other lists within the list item.
And so on.
A custom list is not only a column of projects, but a combination of projects and comments.
The custom list starts with the <DL> label. Each custom list item starts with <DT>. The definition of each custom list item starts with <DD>.
9. html Image
The ALT attribute is used to define a string of prepared replaceable texts for an image. The value of the Replace text attribute is user-defined.
alt="Big Boat">
When the browser cannot load images, replacing the text property tells readers what information they lose. In this case, the browser displays the alternative text instead of the image. Adding Replace text attributes to images on the page is a good habit, which helps to better display information and is very useful for those who use plain text browsers.
10. html background
If you want to use a background image, remember the following points:
- Does the background image increase the page loading time. Tip: image files should not exceed 10 KB.
- Whether the background image works well with other images on the page.
- Whether the background image works well with the text color on the page.
- After the image is tiled in the page, does it look okay?
- Is the focus on text overwhelmed by background images?
<Body> bgcolor
), Background (Background
) And text (Text
Attributes have been deprecated in the latest HTML standard (html4 and XHTML ).
. W3C has deleted these attributes in their recommendation standards.
Use Cascading Style Sheets (CSS)
To define the layout and display attributes of HTML elements.
11. html framework
By using the framework, you can display more than one page in the same browser window. Each HTML document is called a framework, and each framework is independent of other frameworks.
Disadvantages of using the framework:
- Developers must keep track of more HTML documents at the same time.
- Hard to print the entire page
Framework Structure tag (<frameset>)
- Framework Structure tag (<frameset>) defines how to split a window into a framework
- Each frameset defines a series of rows.Or
Column
- The value of rows/columns specifies the area on the screen occupied by each row or column.
Frame)
The frame tag defines the HTML document placed in each frame.
Important:
The <body> </body> label and
<Frameset> </frameset> labels are used at the same time! However, if you add
<Noframes> label, the text must be embedded in the <body> </body> label.
Stop using style properties within HTML tags.
Use lowercase letters to write tags. Remember to close the tag. Never end a paragraph without the </P> label.
12. Verify the HTML file
The HTML document is verified according to the document type declaration. If you want the HTML file to be correctly verified, add the appropriate DTD to the first line of the file.
HTML 4.01 strict DTD
Contains elements and attributes that are not used in opposition or are not included in the Framework:
<!DOCTYPE HTML PUBLIC"-//W3C//DTD HTML 4.01//EN""http://www.w3.org/TR/html4/strict.dtd">
HTML 4.01 transitional DTD
Contains all content in the strict DTD, and elements and attributes used in opposition:
<!DOCTYPE HTML PUBLIC"-//W3C//DTD HTML 4.01 Transitional//EN""http://www.w3.org/TR/html4/loose.dtd">
HTML 4.01 frameset DTD
Contains all content in the transitional DTD, and supports the framework:
<!DOCTYPE HTML PUBLIC"-//W3C//DTD HTML 4.01 Frameset//EN""http://www.w3.org/TR/html4/frameset.dtd">
13. character entity
The character entity consists of one and number (&), one entity name, or #, and one entity number, and a semicolon (;).
To display the minor sign in the HTML document, we need to write as follows:& Lt;
Or& #60;
The most common character entity
Display result |
Description |
Entity name |
Entity ID |
|
Space |
& Nbsp; |
& #160; |
< |
Yu no. |
& Lt; |
& #60; |
> |
Yu no. |
& Gt; |
& #62; |
& |
And number |
& Amp; |
& #38; |
" |
Quotation marks |
& Quot; |
& Amp; #34; |
' |
Marker |
& Apos; (not supported by IE) |
& Amp; #39; |
Other common character entities
Display result |
Description |
Entity name |
Entity ID |
Bytes |
Minute |
& Cent; |
& #162; |
£. |
Pound |
& Pound; |
& #163; |
¥ |
Yen |
& Yen; |
& #165; |
§ |
Section |
& Sect; |
& #167; |
|
Copyright |
& Copy; |
& #169; |
|
Registered Trademark |
& Reg; |
& #174; |
× |
Multiplication number |
& Times; |
& #215; |
Bytes |
Division Number |
& Divide; |
& #247; |
14. Head label
The elements in the header element are not displayed by the browser.
According to the HTML standard, only a few tags are valid in the HTML header. They are: <base>, <link>, <meta>, <title>, <style>, and <SCRIPT>.
<Base> tag
Specify the default address or default target for all links on the page.
Generally, the browser extracts the corresponding elements from the URL of the current document to fill in the blank space in the relative URL.
You can use the <base> label to change the value. The browser will no longer use the URL of the current document, but use the specified basic URL to parse all
URL. These include the URLs in the <A>, , <link>, and <form> labels.
<Meta> tag
<Meta http-equiv = "refresh" content = "5; url = http://www.w3school.com.cn"> redirect to a new address
Developers should not use this technology to force users to switch to different pages, because this will make the page availability worse. Instead, server-side redirection should be used for automatic page orientation.
Note: <meta> the tag is always inside the head element.
Note: Metadata is always transmitted in pairs by name/value.
DTD indicates the DTD in which this attribute is allowed. S = strict, t = transitional, F = frameset.
Required attributes
Attribute |
Value |
Description |
DTD |
Content |
Some_text |
Define metadata related to the HTTP-equiv or name attribute |
STF |
Optional attributes
Attribute |
Value |
Description |
DTD |
HTTP-equiv |
- Content-Type
- Expires
- Refresh
- Set-Cookie
|
Associate the content attribute with the HTTP header. |
STF |
Name |
- Author
- Description
- Keywords
- Generator
- Revised
- Others
|
Associate the content attribute with a name. |
STF |
Scheme |
Some_text |
Defines the format used to translate the content property value. |
STF |
15. html URL (Uniform Resource Locator)
Syntax Rules:
Scheme: // host. Domain: Port/path/filename
Scheme
DefineType
. The most popular type isHTTP
.
Domain
(Domain) define InternetDomain Name
For example, w3school.com.cn.
Host
(Host) defines the host in this domain. If omitted, the default host that supports HTTP isWWW
.
: Port
(Port) defines the host'sPort Number
. The port number is usually omitted. The default port number is80
.
Path
(PATH) definesPath
(A secondary path ). If the path is omitted, the resource (document) is located in the root directory of the website.
Filename
(File Name) Name of the definition document. The default file name is usually default. asp or index.html, or based on other file names set by the Web server.
The full name of the URL is uniform resource locator ".
16. HTML Script
Use the <SCRIPT> label for definition. Note that you can use the type attribute to specify the script language.
Methods To deal with earlier browsers:
Javascript:
<MCE: Script Type = "text/JavaScript"> <! -- <Br/> document. Write ("Hello world! ") <Br/> // --> </MCE: SCRIPT>
17. html 4.0 event attributes
One of the new features of HTML 4 is that HTML events can trigger browser behavior.
Valid only in the body and frameset elements.
Window events)
Attribute |
Value |
Description |
Onload |
Script |
Execute the script when the document is loaded. |
OnUnload |
Script |
Run the script when the document is uninstalled. |
Valid only in form elements.
Form element event (form Element events)
Attribute |
Value |
Description |
Onchange |
Script |
Execute the script when the element changes. |
Onsubmit |
Script |
Execute the script when the form is submitted. |
Onreset |
Script |
Execute the script when the form is reset. |
Onselect |
Script |
Execute the script when the element is selected. |
Onblur |
Script |
Execute the script when the element loses focus |
Onfocus |
Script |
Execute the script when the element gets focus |
This attribute can be used for IMG elements:
Image events)
Attribute |
Value |
Description |
Onabort |
Script |
Execute scripts when image loading is interrupted |
The following elements are invalid: Base, BDO, BR, frame, frameset, Head, HTML, IFRAME, Meta, Param, script, style, and title.
Keyboard Events)
Attribute |
Value |
Description |
Onkeydown |
Script |
Execute the script when the keyboard is pressed |
Onkeypress |
Script |
Execute the script when the keyboard is pressed and loose. |
Onkeyup |
Script |
Execute the script when the keyboard is released |
The following elements are invalid: Base, BDO, BR, frame, frameset, Head, HTML, IFRAME, Meta, Param, script, style, and title.
Mouse events)
Attribute |
Value |
Description |
Onclick |
Script |
Execute the script when the mouse is clicked |
Ondblclick |
Script |
Execute the script when the mouse is double-clicked. |
Onmousedown |
Script |
Execute the script when the mouse button is pressed |
Onmousemove |
Script |
Execute the script when the mouse pointer moves |
Onmouseout |
Script |
Execute the script when the mouse pointer removes an element. |
Onmouseover |
Script |
Execute the script when the cursor is hovering over an element. |
Onmouseup |
Script |
Execute the script when the mouse button is released |