What is the purpose of the element?

To use HTML button elements to achieve clickable buttons, you must first master its basic usage and common precautions. 1. Create buttons with tags and define behaviors through type attributes (such as button, submit, reset), which is submitted by default; 2. Add interactive functions through JavaScript, which can be written inline or bind event listeners through ID to improve maintenance; 3. Use CSS to customize styles, including background color, border, rounded corners and hover/active status effects to enhance user experience; 4. Pay attention to common problems: make sure that the disabled attribute is not enabled, JS events are correctly bound, layout occlusion, and use the help of developer tools to troubleshoot exceptions. Master this

Metadata in HTMLhead is crucial for SEO, social sharing, and browser behavior. 1. Set the page title and description, use and keep it concise and unique; 2. Add OpenGraph and Twitter card information to optimize social sharing effects, pay attention to the image size and use debugging tools to test; 3. Define the character set and viewport settings to ensure multi-language support is adapted to the mobile terminal; 4. Optional tags such as author copyright, robots control and canonical prevent duplicate content should also be configured reasonably.

Using HTML sums allows for intuitive and semantic clarity to add caption text to images or media. 1. Used to wrap independent media content, such as pictures, videos or code blocks; 2. It is placed as its explanatory text, and can be located above or below the media; 3. They not only improve the clarity of the page structure, but also enhance accessibility and SEO effect; 4. When using it, you should pay attention to avoid abuse, and apply to content that needs to be emphasized and accompanied by description, rather than ordinary decorative pictures; 5. The alt attribute that cannot be ignored, which is different from figcaption; 6. The figcaption is flexible and can be placed at the top or bottom of the figure as needed. Using these two tags correctly helps to build semantic and easy to understand web content.

class, id, style, data-, and title are the most commonly used global attributes in HTML. class is used to specify one or more class names to facilitate style setting and JavaScript operations; id provides unique identifiers for elements, suitable for anchor jumps and JavaScript control; style allows for inline styles to be added, suitable for temporary debugging but not recommended for large-scale use; data-properties are used to store custom data, which is convenient for front-end and back-end interaction; title is used to add mouseover prompts, but its style and behavior are limited by the browser. Reasonable selection of these attributes can improve development efficiency and user experience.

Native lazy loading is a built-in browser function that enables lazy loading of pictures by adding loading="lazy" attribute to the tag. 1. It does not require JavaScript or third-party libraries, and is used directly in HTML; 2. It is suitable for pictures that are not displayed on the first screen below the page, picture gallery scrolling add-ons and large picture resources; 3. It is not suitable for pictures with first screen or display:none; 4. When using it, a suitable placeholder should be set to avoid layout jitter; 5. It should optimize responsive image loading in combination with srcset and sizes attributes; 6. Compatibility issues need to be considered. Some old browsers do not support it. They can be used through feature detection and combined with JavaScript solutions.

The main difference is that textarea supports multiple lines of text input, while inputtext is only available in a single line. 1. Use inputtype="text" to be suitable for short and single-line user input, such as username, email address, etc., and can set maxlength to limit the number of characters. The browser provides automatic filling function, making it easier to uniformly style across browsers; 2. Use textarea for scenarios that require multiple lines of input, such as comment boxes, feedback forms, support line breaks and paragraphs, and can control the size through CSS or disable the adjustment function. Both support form features such as placeholders and required fills, but textarea defines the size through rows and cols, and input uses the size attribute.

Using HTML tags, you can use the href attribute to realize page jump, open new windows, positioning within pages and email and phone link functions. 1. Basic usage: Specify the target address through href, such as accessing a web page; 2. Open a new window: add target="_blank" and rel="noopener" attributes; 3. Jump within the page: combine id and # symbol to achieve anchor point positioning; 4. Email phone link: use mailto: or tel: protocol to trigger system applications.

srcset and sizes are key properties for HTML implementation of responsive images. srcset provides multiple image sources and their width or pixel density, such as 400w and 800w, and the browser selects the appropriate image accordingly; sizes defines the display width of the image under different screen widths, such as (max-width: 600px)100vw, 50vw, so that the browser can more accurately match the image size. In actual use, you need to prepare multi-size pictures, clearly named, design layout in accordance with media query, and test the performance of the equipment to avoid ignoring sizes or unit errors, thereby saving bandwidth and improving performance.