Value format specification

CSS value format specifications are crucial for code consistency and maintainability. Color values should use lowercase hexadecimal shorthand. RGB and RGBA require spaces and should omit leading zeros in opacity. Omit units for zero lengths, but non-zero values must include units. Percentage values should not use decimals. Font stacks must include generic family names, font sizes should use rem units, and line heights are recommended as unitless numbers. Animation keyframes should use integer percentages, with time units uniformly in seconds. Multi-parameter functions should align line breaks with spaces after commas. Media query breakpoints should use predefined variables. Custom property names should be lowercase with hyphen separation. Avoid manually writing browser prefixes. Global keywords require comments explaining their purpose. Responsive image handling needs clear descriptors. Feature detection should fully test properties and values. These specifications enhance team collaboration efficiency, reduce style conflicts, and improve code readability.

The order of attribute writing

The order of writing CSS properties is crucial for code readability and maintainability. A well-structured sequence makes stylesheets easier to understand and reduces confusion in team collaboration. General principles recommend grouping properties by functionality: layout properties, box model properties, text-related properties, visual decoration properties, and other properties. Detailed classifications include layout and positioning, box model, typography, background, border, interaction, animation, etc. Special cases involve handling vendor prefix ordering and grouping related properties. Tools like Stylelint are recommended for automated sorting. Team collaboration requires establishing unified standards, considering framework compatibility and tool support. A practical example demonstrates the property ordering for an e-commerce product card. In terms of performance optimization, a logical sequence improves reusability and reduces redundancy. Historically, the evolution shifted from alphabetical order to type-based grouping as the mainstream. Personal habits should conform to team standards, enforced through training and code reviews to ensure consistency. While proper property ordering does not affect rendering performance, it significantly enhances development efficiency and maintainability.

Image blur technique: img { filter: blur(5px); }

The CSS `filter` property's `blur()` function can easily achieve image blur effects by setting the blur radius—the larger the value, the more pronounced the effect. The basic usage involves applying `filter: blur(5px)` directly to an element. Hover interactions can be implemented using the `:hover` pseudo-class to remove the blur. It can also be used for background images, but note that the container needs proper styling. Performance-wise, excessive use may impact page speed, especially on low-end devices. Browser compatibility is excellent, with modern browsers supporting it, and adding the `-webkit-` prefix ensures broader compatibility. Advanced techniques include combining multiple filters to create frosted glass effects. Practical applications include image loading placeholders and blurring sensitive content. Alternatives include Canvas and SVG filters. In responsive design, the blur intensity can be adjusted based on screen size. It can also be combined with CSS animations to create dynamic effects. Note that blurring affects child elements and print outcomes.

Force the scrollbar to always display: html { overflow-y: scroll; }

Forcing the scrollbar to always display can be achieved with the CSS rule `html { overflow-y: scroll; }`. When the page content height is less than the viewport height, browsers typically hide the vertical scrollbar by default. This dynamic behavior can cause layout shifts and inconsistent user experiences. The simplest implementation is to apply this CSS rule to the `html` element, which forces the browser to always display the vertical scrollbar, regardless of whether the content exceeds the viewport. This approach is more efficient than using JavaScript solutions. The `overflow-y` property has several possible values: `visible` (default), `hidden` (clips overflow content), `scroll` (always shows the scrollbar), and `auto` (lets the browser decide). Forcing the scrollbar prevents layout shifts, allows better custom styling, and maintains layout stability. All modern browsers support this property. In responsive design, scrollbar policies can be adjusted for different devices. The performance impact of forcing scrollbars is negligible, but it can be included as a foundational style in design systems. Considerations include interactions with other CSS features and accessibility implications. Alternatives to `overflow-y: scroll` include JavaScript-based solutions. Note that scrollbar widths may vary across systems, requiring unified handling. The CSS Scrollbars specification offers more control, and popular frameworks also provide implementation methods. For testing and debugging, inspect element styles and viewport effects. Common issues include unintended horizontal scrollbars or double scrollbars on mobile. Advanced use cases involve nested scrolling regions and full-screen applications. Performance optimization tips include avoiding excessive nested scroll containers. Future CSS features will introduce more scrollbar control, such as the `scrollbar-gutter` property.

Disable user selection: body { user-select: none; }

The `user-select: none` property in CSS controls text selection by users. Setting it to `none` prevents text from being selected, commonly used for copyright protection or enhancing interactive experiences. Its values include `auto` (default), `none` (disables selection), `text` (allows selection), and `all` (selects all with one click). Note browser compatibility and add prefixes when necessary. Practical applications include preventing copying, optimizing drag-and-drop interfaces, and game UIs, though it cannot fully block content access via developer tools. It may impact accessibility and can be dynamically controlled with JavaScript or combined with other CSS properties like `cursor`. An example demonstrates implementing non-selectable cards, or partial selectability by overriding parent settings with child elements. Performance impact is minimal.

Element vanishing spell: div { display: none !important; }

`display: none !important` is a CSS declaration that forcibly hides an element, completely removing it from the layout and making it invisible without occupying space. It also hides all child elements and disables their interactive functionality. The `!important` flag increases the style's priority to ensure the rule takes effect, commonly used to override third-party styles or control responsive layouts. However, it may cause accessibility issues, dynamic interaction limitations, and debugging difficulties. Alternatives include visual hiding techniques or conditional rendering. Compared to other hiding methods, `display: none` does not affect layout and offers better rendering performance. In framework components and CSS-in-JS, it has special implementations. Browsers skip rendering calculations for such elements. When debugging, be mindful of the impact of the `!important` flag. Proper use can optimize SPA performance and control printed content, but accessibility and maintenance costs must be weighed.

One-click dark mode: html { filter: invert(1); }

Using the `filter: invert(1)` to implement dark mode on a webpage is a quick and easy method that inverts all colors, such as turning white to black, black to white, red to cyan. By adding `hue-rotate(180deg)`, the hue can remain unchanged. The article details the basic implementation, how to handle image issues, and advanced techniques for using it with CSS variables. It also discusses browser compatibility, performance considerations, and interactions with other CSS features. Solutions are provided for special cases like form elements, shadow effects, and SVG icons in real-world projects. Additionally, it compares the pros and cons with traditional dark mode implementations and explores applications in responsive design frameworks and server-side rendering. Finally, it looks ahead to potential future CSS improvements for better dark mode implementation.

Selector usage specification

CSS selector types include element selectors, class selectors, ID selectors, attribute selectors, and pseudo-class selectors. Selector combination methods include descendant selectors, child selectors, adjacent sibling selectors, general sibling selectors, and multiple selectors. Priority rules determine style application by calculating weights, with inline styles, ID selectors, class selectors, element selectors, and wildcards corresponding to different weights. `!important` can be used to elevate priority. For performance optimization, avoid over-qualifying selectors, minimize wildcards, prioritize class selectors, and avoid deep nesting. The BEM naming convention divides styles into blocks, elements, and modifiers to improve maintainability. Responsive design should follow the mobile-first principle and use media queries appropriately. In preprocessors, nested selectors should control depth to avoid excessive nesting, and parent selector references can simplify code.

Naming conventions (BEM/OOCSS, etc.)

The BEM naming convention divides interfaces into independent blocks, elements, and modifiers, strictly resolving CSS scoping issues. The OOCSS methodology treats styles as reusable objects, separating structure from skin, and containers from content. The SMACSS approach categorizes CSS rules into five types: base, layout, module, state, and theme. The ITCSS architecture organizes code hierarchically based on CSS specificity, managing complexity from generic to specific. The ACSS methodology advocates creating small utility classes for individual properties, composing them to build UIs. The SUIT CSS naming convention combines BEM concepts with utility and state classes, making it suitable for component-based frameworks. When selecting a CSS naming convention, consider project scale, team preference, and tech stack. Small projects suit BEM or OOCSS, while large applications benefit from SMACSS or ITCSS. Component-based frameworks align well with SUIT CSS or BEM variants, and rapid prototyping favors ACSS or Tailwind CSS. Consistency is key—teams should establish clear guidelines and enforce them strictly.

File organization structure

The organization of CSS file structure is crucial for code maintainability and readability. A reasonable division of files enables quick location of style rules and reduces team collaboration costs. A typical project should include core files such as base styles, component styles, and layout styles. The main entry file aggregates other parts via imports, adopting a modular organization that may use BEM naming conventions or atomic CSS approaches. Variable management requires a dedicated file. Responsive code organization can follow either centralized or decentralized approaches. Third-party styles should be stored separately with clear override hierarchies. Splitting CSS by routes enables code splitting, while style documentation aids team understanding. Build output requires configuration for different environments, and style validation is achieved via Stylelint. Performance optimizations include critical CSS extraction. Theme switching is implemented through multi-theme file structures, and style debugging can be enhanced with environment markers. These practices collectively build an efficient and maintainable CSS architecture.