href: hypertext reference, used on elements such as link and a. href is a reference and page association, establishing a connection between the current element and the referenced resource.

src: represents a reference resource, replaces the current element, and is used in img, script, and iframe.

Strict mode: Run at the highest standard supported by the browser

Mixed mode: The page is displayed in a loosely backward-compatible manner, simulating the behavior of older browsers

Progressive enhancement: ensure the most basic functions at the beginning, and then improve and add

Graceful degradation: build full functionality from the beginning and then make it compatible with older browsers

img title and alt

The difference between title and h1

The difference between b and strong, the difference between i and em

DOM is the document object model, html document

BOM is the browser object model, which operates the API that appears in the browser (window, etc.)

Function: Make the width of the current viewport equal to the width of the device, while not allowing the user to manually zoom

Principle: Mobile browsers usually render pages in a virtual window that is wider than the mobile screen. This virtual window is the viewport; the purpose is to display web pages that are not mobile-adapted normally so that they can be fully displayed to the user;

Availability

accessibility

maintainability

accesskey: Set shortcut keys to provide quick access

class: class

contenteditable: The specified element is editable

contextnemu: Customize the content of the right-click mouse pop-up menu

data-*: Add custom attributes to elements

dir: Set the element text direction

draggable: Set whether the element can be dragged

dropzone; set element drag and drop type

hidden: set hidden

id: unique identifier

lang: language

spellcheck: whether to enable spelling and grammar checking

style: inline css style

title: Suggested information related to the element

translate: Whether the content of elements and descendant nodes needs to be localized

canvas: Draw 2D graphics through JavaScript.

SVG: A language for describing 2D graphics using XML.

Add new element

CanvasCanvas

Media video, audio

Geo API

local storage

Offline application

form

File API

Drag and drop API

Communication API

Web Workers processing threads

Tell the browser which HTML or XHTML specification the document uses; tell the browser according to which specification to parse the page

Do the right thing with the right label

The page content is structured and the structure is clearer

Improve SEO, search engine crawlers rely on html tags

Convenient for reading and later maintenance