positioning — 100.00% verified visual parity

clear:both pushes the cleared block below preceding floats instead of wrapping beside them.

Absolute box resolves against the nearest positioned ancestor, skipping intermediate static parents.

A transform on a non-positioned ancestor makes it the containing block for an absolute descendant.

float:left removes the box from flow and shifts it left; the following block wraps around its right side.

Absolute top/right/bottom/left percentages resolve against the containing block and stretch the child to the centered half-size box; catches pixel interpretation or wrong percentage bases.

position:relative with negative top/left pulls the box up and left, overlapping prior flow.

The inset shorthand stretches an absolutely positioned box with inset:20px 30px 40px 50px; catches parsers that ignore the shorthand while longhands work.

Logical inset longhands map to physical top/right/bottom/left in horizontal-tb writing mode; catches ignoring logical inset properties or mapping axes incorrectly.

All four insets set with auto size make an absolute box stretch to fill the containing block inset by 30px.

overflow:hidden on a positioned ancestor clips an absolutely positioned descendant past the clip edges.

overflow:hidden clips an oversized in-flow child to the parent box.

overflow:visible (default) does not clip; the child overflows the parent box.

An absolute non-visual parent keeps its top and left offsets when its only content is a normal-flow block child.

position:fixed header repeats at the top of each printed page; catches treating fixed as a one-page absolute box.

position:fixed box placed by top/left relative to the page box on a single non-scrolling page.

position:absolute box anchored to bottom/right edges of its containing block.

position:absolute box placed by top/left within a relative containing block.

position:relative shifts the box by top/left from its in-flow position; flow space is preserved.

position:static box ignores top/left offsets and stays in normal flow.

position:relative percentage top/left offsets resolve against the containing block and cover the red marker; catches own-size percentage bases or ignored relative percentages.

A positioned z-index:-1 child in a local stacking context stays behind an overlapping in-flow sibling; catches painting all positioned descendants above normal flow.

Without z-index, positioned siblings stack in source order; the later box paints over the earlier.

Higher z-index paints on top of a later-in-source sibling with lower z-index.