There are three ways to selectively include CSS on a specific page: 1. Inline CSS, suitable for pages that are not frequently accessed or require unique styles; 2. Load external CSS files using JavaScript conditions, suitable for situations where flexibility is required; 3. Containment on the server side, suitable for scenarios using server-side languages. This approach can optimize website performance and maintainability, but requires balance of modularity and performance.

CSS blocks page rendering because browsers view inline and external CSS as key resources by default, especially with imported stylesheets, header large amounts of inline CSS, and unoptimized media query styles. 1. Extract critical CSS and embed it into HTML; 2. Delay loading non-critical CSS through JavaScript; 3. Use media attributes to optimize loading such as print styles; 4. Compress and merge CSS to reduce requests. It is recommended to use tools to extract key CSS, combine rel="preload" asynchronous loading, and use media delayed loading reasonably to avoid excessive splitting and complex script control.

The overflow attribute handles overflow content by hiding, scrolling or automatically adjusting. The main values ??include 1. Hidden direct cropping; 2. Scroll always displays scroll bars; 3. Auto displays scroll bars as needed; 4. Overflow-x and overflow-y can control horizontal and vertical overflow respectively. 1. overflow:hidden is used to avoid overflow of content; 2. overflow:scroll is suitable for chat windows or fixed-size sidebars to keep the interface consistent; 3. overflow:auto is suitable for tables or user-generated content to achieve flexible scrolling; 4. Note when setting overflow-x and overflow-y independently

ToimplementdarkmodeinCSSeffectively,useCSSvariablesforthemecolors,detectsystempreferenceswithprefers-color-scheme,addamanualtogglebutton,andhandleimagesandbackgroundsthoughtfully.1.DefineCSSvariablesforlightanddarkthemestomanagecolorsefficiently.2.Us

Vertical centering content can be implemented in CSS in a variety of ways, the most direct way is to use Flexbox. 1. Use Flexbox: By setting the container to display:flex and in conjunction with align-items:center, vertical centering of child elements can be easily achieved; 2. Combination of absolute positioning and transform: suitable for absolute positioning elements, by setting top and left to 50% and then using translate (-50%,-50%) to achieve centering; 3. CSSGrid: Through display:grid and place-items:center, horizontal and vertical centering can be achieved at the same time. If only vertical centering is required, use align

The topic differencebetweenem, Rem, PX, andViewportunits (VH, VW) LiesintheirreFerencepoint: PXISFixedandbasedonpixelvalues, emissrelative EtothefontsizeFheelementoritsparent, Remisrelelatotherootfontsize, AndVH/VwarebaseDontheviewporttimensions.1.PXoffersprecis

ThebestapproachforCSSdependsontheproject'sspecificneeds.Forlargerprojects,externalCSSisbetterduetomaintainabilityandreusability;forsmallerprojectsorsingle-pageapplications,internalCSSmightbemoresuitable.It'scrucialtobalanceprojectsize,performanceneed

No,CSSdoesnothavetobeinlowercase.However,usinglowercaseisrecommendedfor:1)Consistencyandreadability,2)Avoidingerrorsinrelatedtechnologies,3)Potentialperformancebenefits,and4)Improvedcollaborationwithinteams.