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.

The main difference between window.onload and DOMContentLoaded is the trigger timing. DOMContentLoaded is fired immediately after HTML parsing is completed, and does not wait for the stylesheet, picture and subframe to load; while window.onload waits for all resources (including pictures and external resources) to be loaded before execution. 1. Use DOMContentLoaded when the code only requires HTML structure to be ready, such as selecting elements, setting event listeners, or modifying the DOM tree; 2. Use window.onload when the script relies on all external resources to load, such as reading image sizes or preloading resources. Note: window.onload assignment

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

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.