When using HTML5SSE, the methods to deal with reconnection and errors include: 1. Understand the default reconnection mechanism. EventSource retrys 3 seconds after the connection is interrupted by default. You can customize the interval through the retry field; 2. Listen to the error event to deal with connection failure or parsing errors, distinguish error types and execute corresponding logic, such as network problems relying on automatic reconnection, server errors manually delay reconnection, and authentication failure refresh token; 3. Actively control the reconnection logic, such as manually closing and rebuilding the connection, setting the maximum number of retry times, combining navigator.onLine to judge network status to optimize the retry strategy. These measures can improve application stability and user experience.

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.

To control HTML5 video and audio playback using JavaScript, master the following key operations to achieve basic control. 1. Start or pause play can be achieved through the .play() and .pause() methods, and it is recommended to trigger through user interaction to be compatible with mobile browsers; 2. Control the volume and set the value from 0 to 1 through the volume attribute, and switch by setting the muted attribute to true or false; 3. Jump to a specific time to play, you can use the currentTime attribute, which supports direct assignment or increase or decrease the current time, and it is recommended to add error handling; 4. Listen to the playback status changes can be achieved through events such as play, pause, ended and timeupdate.

Server-SentEvents (SSE) is a lightweight solution provided by HTML5 to push real-time updates to the browser. It realizes one-way communication through long HTTP connections, which is suitable for stock market, notifications and other scenarios. Create EventSource instance and listen for messages when using: consteventSource=newEventSource('/stream'); eventSource.onmessage=function(event){console.log('Received message:',event.data);}; The server needs to set Content-Type to text/event

Doctype is a statement that tells the browser which HTML standard to use to parse the page. Modern web pages only need to be written at the beginning of the HTML file. Its function is to ensure that the browser renders the page in standard mode rather than weird mode, and must be located on the first line, with no spaces or comments in front of it; there is only one correct way to write it, and it is not recommended to use old versions or other variants; other such as charset, viewport, etc. should be placed in part.

To build standardized and clear HTML5 documents, the following best practices must be followed: 1. Use standard document type declarations; 2. Build a basic skeleton including three tags and pay attention to the character set, title and script location; 3. Use semantic tags such as , , to improve accessibility and SEO; 4. Reasonably nest the title levels to ensure that the structure is clear and there is only one per page. These steps help improve code quality, collaboration efficiency and user experience.

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.

Using HTML5 semantic tags and Microdata can improve SEO because it helps search engines better understand page structure and content meaning. 1. Use HTML5 semantic tags such as,,,, and to clarify the function of page blocks, which helps search engines establish a more accurate page model; 2. Add Microdata structured data to mark specific content, such as article author, release date, product price, etc., so that search engines can identify information types and use them for display of rich media summary; 3. Pay attention to the correct use of tags to avoid confusion, avoid duplicate tags, test the effectiveness of structured data, regularly update to adapt to changes in schema.org, and combine with other SEO means to optimize for long-term.