Css Z Index.md

notes:

• z-index need to add position relative or above
• z-index calculate from its parent that with z-index
• z-index auto do not measure

edge case 1:

• layer 1 (z-index: 2), layer 1-1 (z-index: 99)
• layer 2 (z-index: 1), layer 2-1 (z-index: 99999)
• result: layer 1-1 shows on top

edge case 2:

• layer 1 (z-index: 2), layer 1-1 (z-index: 99)
• layer 2 (z-index: auto), layer 2-1 (z-index: 99999)
• result: layer 2-1 shows on top

test index.html