loading="lazy" is an HTML attribute for and which enables the browser's native lazy loading function to improve page performance. 1. It delays loading non-first-screen resources, reduces initial loading time, saves bandwidth and server requests; 2. It is suitable for large amounts of pictures or embedded content in long pages; 3. It is not suitable for first-screen images, small icons, or lazy loading using JavaScript; 4. It is necessary to cooperate with optimization measures such as setting sizes and compressing files to avoid layout offsets and ensure compatibility. When using it, you should test the scrolling experience and weigh the user experience.

When writing legal and neat HTML, you need to pay attention to clear structure, correct semantics and standardized format. 1. Use the correct document type declaration to ensure that the browser parses according to the HTML5 standard; 2. Keep the tag closed and reasonably nested to avoid forgetting closed or wrong nesting elements; 3. Use semantic tags such as, etc. to improve accessibility and SEO; 4. The attribute value is always wrapped in quotes, and single or double quotes are used uniformly. Boolean attributes only need to exist, and the class name should be meaningful and avoid redundant attributes.

The web page structure needs to be supported by core HTML elements. 1. The overall structure of the page is composed of , , which is the root element, which stores meta information and displays the content; 2. The content organization relies on title (-), paragraph () and block tags (such as ,) to improve organizational structure and SEO; 3. Navigation is implemented through and implemented, commonly used organizations are linked and supplemented with aria-current attribute to enhance accessibility; 4. Form interaction involves , , and , to ensure the complete user input and submission functions. Proper use of these elements can improve page clarity, maintenance and search engine optimization.

Client-sideformvalidationcanbedonewithoutJavaScriptbyusingHTMLattributes.1)Userequiredtoenforcemandatoryfields.2)ValidateemailsandURLswithtypeattributeslikeemailorurl,orusepatternwithregexforcustomformats.3)Limitvaluesusingmin,max,minlength,andmaxlen

When Nginx experiences a "Toomyopenfiles" error, it is usually because the system or process has reached the file descriptor limit. Solutions include: 1. Increase the soft and hard limits of Linux system, set the relevant parameters of nginx or run users in /etc/security/limits.conf; 2. Adjust the worker_connections value of Nginx to adapt to expected traffic and ensure the overloaded configuration; 3. Increase the upper limit of system-level file descriptors fs.file-max, edit /etc/sysctl.conf and apply changes; 4. Optimize log and resource usage, and reduce unnecessary file handle usage, such as using open_l

To enable Nginx's HTTP/2 or HTTP/3 support, the prerequisites must be met and configured correctly; HTTP/2 requires Nginx1.9.5, OpenSSL1.0.2 and HTTPS environment; add --with-http_v2_module module during configuration, modify the listening statement to listen443sslhttp2; and overload the service; HTTP/3 is based on QUIC, and third-party modules such as nginx-quic are required to introduce BoringSSL or OpenSSLQUIC branches during compilation, and configure UDP listening ports; common problems during deployment include ALPN not enabled, certificate incompatible, firewall restrictions and compilation errors, it is recommended to use priority

Notes on using HTML tags: 1. It must be accompanied by title attribute to define the complete meaning of the abbreviation, such as HTML; 2. Use uniformly instead of discarded tags; 3. Use only when necessary, avoid nesting, and adjust the default style through CSS to improve accessibility and SEO effects.

The function is to display structured two-dimensional data, such as score sheets, timetables, etc.; it is not used for page layout. The correct way to use it includes: 1. wrap the entire table with it; 2. define the table header; 3. contain the main content; 4. represent a row; 5. or define a cell. Auxiliary tags include: add title; define column attributes; display the bottom summary information. Notes: Avoid complex structures, reduce the number of columns to improve the mobile experience, and use a responsive framework to optimize the display effect.