html - child with 100% width in padding applied parent -

i have div css specifications:

width:200px; padding:5px border:1px solid

and div it's child css:

width:100% border:1px solid

and these divs has rendered in ff , ie this:
enter image description here

but seems right padding less left one! can 1 tell me why behavior causes?

this happens because borders of inner div not part of definition of width itself, inner div 100% + 2px wide.

you should specify box-sizing: border-box; inner div, width include borders

see mdn documentation further information (and browser support) property.

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