It is a semantic tag used in HTML5 to define the bottom of the page or content block, usually including copyright information, contact information or navigation links; it can be placed at the bottom of the page or nested in, etc. tags as the end of the block; when using it, you should pay attention to avoid repeated abuse and irrelevant content.

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.

To create HTML paragraphs, you need to use tags, which are used to organize text content into separate paragraph blocks, improving readability, style control, and accessibility. When used, start with and close, and the paragraphs are line-breaked by default and have spacing; simulated paragraphs cannot be nested or abused. In addition, you can unify or differentiate styles through CSS and improve SEO and accessibility. Correct use helps clear content structure and facilitates search engine analysis.

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

Use tags in HTML to group options in the drop-down menu. The specific method is to wrap a group of elements and define the group name through the label attribute, such as: 1. Contains options such as apples, bananas, oranges, etc.; 2. Contains options such as carrots, broccoli, etc.; 3. Each is an independent group, and the options within the group are automatically indented. Notes include: ① No nesting is supported; ② The entire group can be disabled through the disabled attribute; ③ The style is restricted and needs to be beautified in combination with CSS or third-party libraries; plug-ins such as Select2 can be used to enhance functions.

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.