How to add a background image in html and make the image tile the entire page? (code example)

vw and vh units achieve responsive design by associating element sizes with viewport width and height; 1vw is equal to 1% of viewport width, and 1vh is equal to 1% of viewport height; commonly used in full screen area, responsive fonts and elastic spacing; 1. Use 100vh or better 100dvh in the full screen area to avoid the influence of the mobile browser address bar; 2. Responsive fonts can be limited with 5vw and combined with clamp (1.5rem, 3vw, 3rem) to limit the minimum and maximum size; 3. Elastic spacing such as width:80vw, margin:5vhauto, padding:2vh3vw, can make the layout adaptable; pay attention to mobile device compatibility, accessibility and fixed width content conflicts, and it is recommended to give priority to using dvh first;

Theaspect-ratioCSSpropertydefinesthewidth-to-heightratioofanelement,ensuringconsistentproportionsinresponsivedesigns.1.Itisapplieddirectlytoelementslikeimages,videos,orcontainersusingsyntaxsuchasaspect-ratio:16/9.2.Commonusecasesincludemaintainingres

The:emptypseudo-classselectselementswithnochildrenorcontent,includingspacesorcomments,soonlytrulyemptyelementslikematchit;1.Itcanhideemptycontainersbyusing:empty{display:none;}tocleanuplayouts;2.Itallowsaddingplaceholderstylingvia::beforeor::after,wh

Use a div with border to quickly create vertical lines, and define styles and heights by setting border-left and height; 2. Use ::before or ::after pseudo-elements to add vertical lines without additional HTML tags, suitable for decorative separation; 3. In Flexbox layout, by setting the width and background color of the divider class, adaptive vertical dividers between elastic containers can be achieved; 4. In CSSGrid, insert vertical lines as independent columns (such as autowidth columns) into grid layout, which is suitable for responsive design; the most appropriate method should be selected according to the specific layout needs to ensure that the structure is simple and easy to maintain.

CSS pseudo-class is a keyword used to define the special state of an element. It can dynamically apply styles based on user interaction or document location; 1.:hover is triggered when the mouse is hovered, such as button:hover changes the button color; 2.:focus takes effect when the element gets focus, improving form accessibility; 3.:nth-child() selects elements by position, supporting odd, even or formulas such as 2n 1; 4.:first-child and :last-child select the first and last child elements respectively; 5.:not() excludes elements that match the specified conditions; 6.:visited and:link set styles based on the link access status, but:visited is restricted by privacy.

Use hidden checkboxes and CSS's :checked pseudo-class combined with adjacent sibling selectors ( ) to control content display; 2. The HTML structure contains input, label and content div for each collapsed item; 3. Smooth expansion/collapse animations by setting max-height transition; 4. Add open/close status icons with pseudo-elements; 5. Use radio types to implement single-open mode, while checkbox allows multiple openings. This is an interactive foldable menu implementation that requires no JavaScript and is compatible with modern browsers.

TheCSSfilterpropertyallowsvisualeffectslikeblur,brightness,andgrayscaletobeapplieddirectlytoHTMLelements.1)Usethesyntaxfilter:filter-function(value)toapplyeffects.2)Combinemultiplefilterswithspaceseparation,e.g.,blur(2px)brightness(70%).3)Commonfunct

Use CSS to create dotted borders, just set the border attribute to dotted. For example, "border:3pxdotted#000" can add a 3-pixel-wide black dot border to the element. By adjusting the border-width, the size of the point can be changed. The wider borders produce larger points. You can set dotted borders for a certain side, such as "border-top:2pxdottedred". Dotted borders are suitable for block-level elements such as div and input. They are often used in focus states or editable areas to improve accessibility. Pay attention to color contrast. At the same time, different from dashed's short-line style, dotted presents a circular dot shape. This feature is widely used in all mainstream browsers.