css code to realize the mutual exchange of rows and columns of the table

BEM is a CSS naming specification that improves code readability, reduces conflicts and facilitates maintenance. 1.Block is a separate component, such as .btn; 2.Element is an integral part of Block, such as .nav\_\_link; 3.Modifier represents a state or variant, such as .btn--large. The naming formats are .block, .block\_\_element, .block--modifier or .block\_\_element--modifier respectively. Using BEM can avoid class name conflicts, improve maintainability, and facilitate team collaboration. Notes include: avoiding too deep levels, using Modifier reasonably,

CSS refers to the weighting mechanism used by the browser to determine which style rules are preferred. When multiple rules act on the same element, a high-weight rule takes effect. For example, #mainp is more specific than p, and will cover the color blue. The calculation method is based on the selector type and is divided into four levels: a is the number of inline styles, b is the number of ID selectors, c is the number of classes, attributes, and pseudo-classes, and d is the number of elements and pseudo-elements. Compare bit by bit when comparing, and compare a→b→c→d in sequence like a phone number. Common misunderstandings include abuse!important, over-necking selectors, dependency ID selectors, etc. It is recommended to use clear structure and unified class name naming to reduce conflicts, and you can check the style coverage through the developer tool and adjust the selector rights.

There are four ways to customize mouse pointers using CSS: 1. Use the cursor attribute to set built-in styles, such as pointer, text, etc.; 2. Specify the custom picture as the cursor through url() and set alternate styles; 3. Add coordinate values after url() to adjust the hot spot position of the cursor; 4. Use JavaScript to hide the native cursor and use elements to simulate dynamic effects. Each method is suitable for different scenarios, and needs to pay attention to compatibility, performance and user experience details.

The role of id and class in CSS is different, and the usage scenarios are also different. 1.id is a unique identifier, used for style design of a single unique element, such as #main-content; 2.class can be reused and is suitable for multiple elements to apply the same style, such as .button; 3.id's selector priority is higher than class, which will affect style overwrite; 4. id is used in HTML, class is used in class, 5. id is used in CSS, and class is used in class. 6. It is recommended to avoid excessive use of id for style design, because it is not easy to cover; 7.

To center elements horizontally and vertically, the most common methods include using Flexbox, Grid and absolute positioning to match transform. 1. Use Flexbox: Set the container to flex layout, and set it to center through justify-content and align-items, which is suitable for modern browsers and is simple and efficient; 2. Use Grid: Use display:grid and place-items:center to achieve centering, which is concise and clear; 3. Absolute positioning and transform: suitable for old browsers, set it to 50% by left and top and use transform to move half of its width and height back to achieve centering. It is commonly used

To change the text color in a web page, use the color attribute of CSS. This property controls the foreground color of the text and supports color name, hexadecimal value, RGB or HSL format, such as: p{color:red;} or h1{color:#00ff00;}, which can be applied to label selector, class or ID; commonly used methods include: 1. Color name (such as red); 2. Hexadecimal (such as #ff0000); 3. RGB (such as rgb(255,0,0)); 4. HSL (such as hsl(0,100%,50%)); If the color does not take effect during debugging, it may be overwritten by other rules, insufficient contrast or wrong format. It is recommended to use browser developer tools to check and debug in real time to ensure the effect

ImagereplacementinCSSinvolveshidingrealtextanddisplayinganimageorstyledversioninstead,ensuringaccessibilityandSEObenefitswhileallowingvisualcustomization.1.Theclassicmethodusestext-indenttomovetextoff-screenwhileshowingabackgroundimage,requiringsetel

CSSLogicalProperties and Values provides a layout based on writing mode, using inline, block, start, end and other logical directions to replace the traditional left, right, top, bottom. 1. It enables the style to automatically adapt to LTR, RTL and vertical layout without additional adjustments; 2. Common attributes include margin-inline-start, padding-block-end, inline-size and block-size; 3. Applicable to international websites, component library development and responsive design; 4. Be careful about compatibility when using it, and some browsers may need to fall