定義

用來指定element的定位方式

  • static(default)

    normal flow，top,bottom,left and right properties no effect.

  • relative：

    moving it relative to its position in normal flow

  • fixed

    it fixes an element relative to the browser viewport.

  • absolute

    moves an element completely out of the page’s normal layout flow ,like it is setting on its own separte layer. it is positioned relative to the nearest positioned ancestor(instead of position relative to the viewport,like fixed)

    note：A positioned element is one whose position is anything except static.

  • sticky
    　makes an element act like static until it hits a defined offset from the viewport,at which point it acts like position：fixed.

reference