When an element has a 'position: sticky;' property and scrolls past its container, it sticks to the container until it reaches a specified offset, after which it scrolls along with the container. This behavior is often used for navigation bars.

The animation-fill-mode: forwards; property-value combination holds the final keyframe styles after the animation finishes. This means that after the animation completes, the element retains the styles from the final keyframe. This can be useful for maintaining a particular state after the animation finishes.

The technique where a low-quality or system font is displayed initially and then replaced with a higher-quality custom font when it's loaded is known as "Font FOUT" or "Flash of Unstyled Text." This approach improves perceived performance and ensures a smoother transition between fonts.

When 'box-sizing' is set to 'content-box,' the total width of an element includes padding and border. The content width does not include these, but the total width does.

When you want to generate multiple class or ID variations in SASS, you would typically use placeholder selectors, also known as %placeholders. These selectors allow you to define styles that can be included in other selectors using the @extend directive, promoting reusability and ensuring cleaner CSS output.

Autoprefixing tools, like Autoprefixer, analyze CSS and add or remove vendor prefixes to ensure compatibility across different browsers. They use data from browser user agents (e.g., Chrome, Firefox) to determine which prefixes are required for specific CSS properties.

To create a blur effect on an image using CSS, you can use the filter property with the blur function. For example, filter: blur(5px); would apply a blur effect to the image, where "5px" represents the level of blurriness. This can be adjusted to control the blur intensity.

To ensure that an element remains in the normal document flow and doesn't overlap floated siblings, you should use the clear property with a value other than none. This property specifies which side of an element other floating elements are not allowed.

The CSS rule "ul + ul" is a sibling combinator that targets an unordered list that immediately follows another unordered list in the HTML structure. This is used to style a specific occurrence of an unordered list in relation to another.

The CSS rule "ul > li" specifically targets only the direct child li elements of a ul element. It will not target li elements that are nested further within the hierarchy of the HTML structure.

The CSS pseudo-class :not() is used to select elements that do not match a specific criteria. It is used to exclude elements that would typically be selected by a CSS selector. For example, :not(.classname) selects all elements that do not have the specified class.

To create a smooth heartbeat animation that makes an icon grow and shrink, you should use the scale transformation with CSS animations. This allows you to scale an element up and down smoothly, ensuring it runs seamlessly in both directions.