The reason why ARIA and HTML5 semantic tags are needed is that although HTML5 semantic elements have accessibility meanings, ARIA can supplement semantics and enhance auxiliary technology recognition capabilities. For example, when legacy browsers lack support, components without native tags (such as modal boxes), and state updates need to be dynamically updated, ARIA provides finer granular control. HTML5 elements such as nav, main, aside correspond to ARIArole by default, and do not need to be added manually unless the default behavior needs to be overridden. The situations where ARIA should be added include: 1. Supplement the missing status information, such as using aria-expanded to represent the button expansion/collapse status; 2. Add semantic roles to non-semantic tags, such as using div role to implement tabs and match them

HTML5, CSS and JavaScript should be efficiently combined with semantic tags, reasonable loading order and decoupling design. 1. Use HTML5 semantic tags, such as improving structural clarity and maintainability, which is conducive to SEO and barrier-free access; 2. CSS should be placed in, use external files and split by module to avoid inline styles and delayed loading problems; 3. JavaScript is recommended to be introduced in front, and use defer or async to load asynchronously to avoid blocking rendering; 4. Reduce strong dependence between the three, drive behavior through data-* attributes and class name control status, and improve collaboration efficiency through unified naming specifications. These methods can effectively optimize page performance and collaborate with teams.

Common reasons why HTML5 videos don't play in Chrome include format compatibility, autoplay policy, path or MIME type errors, and browser extension interference. 1. Videos should be given priority to using MP4 (H.264) format, or provide multiple tags to adapt to different browsers; 2. Automatic playback requires adding muted attributes or triggering .play() with JavaScript after user interaction; 3. Check whether the file path is correct and ensure that the server is configured with the correct MIME type. Local testing is recommended to use a development server; 4. Ad blocking plug-in or privacy mode may prevent loading, so you can try to disable the plug-in, replace the traceless window or update the browser version to solve the problem.

Using HTML5 semantic tags can improve web structure clarity, accessibility and SEO effects. 1. Semantic tags such as,,,, and make it easier for the machine to understand the page content; 2. Each tag has a clear purpose: used in the top area, wrap navigation links, include core content, display independent articles, group relevant content, place sidebars, and display bottom information; 3. Avoid abuse when using it, ensure that only one per page, avoid excessive nesting, reasonable use and in blocks. Mastering these key points can make the web page structure more standardized and practical.

Embed web videos using HTML5 tags, supports multi-format compatibility, custom controls and responsive design. 1. Basic usage: add tags and set src and controls attributes to realize playback functions; 2. Support multi-formats: introduce different formats such as MP4, WebM, Ogg, etc. through tags to improve browser compatibility; 3. Custom appearance and behavior: hide default controls and implement style adjustment and interactive logic through CSS and JavaScript; 4. Pay attention to details: Set muted and autoplay to achieve automatic playback, use preload to control loading strategies, combine width and max-width to achieve responsive layout, and use add subtitles to enhance accessibility.

It is a block-level element, suitable for layout; it is an inline element, suitable for wrapping text content. 1. Exclusively occupy a line, width, height and margins can be set, which are often used in structural layout; 2. No line breaks, the size is determined by the content, and is suitable for local text styles or dynamic operations; 3. When choosing, it should be judged based on whether the content needs independent space; 4. It cannot be nested and is not suitable for layout; 5. Priority is given to the use of semantic labels to improve structural clarity and accessibility.

Yes, you can save its contents as an image using the HTML5Canvas built-in toDataURL() method. First, call canvas.toDataURL ('image/png') to convert the canvas content to a base64 string in PNG format; if JPEG or WebP format is required, the corresponding type and quality parameters such as canvas.toDataURL ('image/jpeg', 0.8) can be passed in. Then you can achieve download by creating a dynamic link and triggering a click event: 1. Create an element a; 2. Set the download attribute and href as image data; 3. Call the click() method. Note that this operation should be triggered by user interaction.

To obtain user location information, you must first obtain authorization. When using HTML5's GeolocationAPI, the first step is to request user permission. If the user refuses or fails to respond, an error should be handled and a prompt should be given; after successful authorization, the Position object includes coords (latitude, longitude, etc.) and timestamp; you can use watchPosition to monitor location changes, but you need to pay attention to performance issues and clear the listener in time. 1. Authorization requires the user to explicitly allow it to trigger the getCurrentPosition method request; 2. Process error.code when rejected or errored and prompt the user; 3. After success, position.coords provides location data; 4.watc