left和top属性根据元素与页面左上角的相对位置定位元素。
The left and top attributes position the element with respect to the upper-left corner of the page.
方位，相对位置：方向，尤指用地理学的或天体图线测量的从一个固定位置到另一个位置的带有角度的方向。
Direction, especially angular direction measured from one position to another using geographical or celestial reference lines.
本发明很容易改变和准确定位掀盖或掀开侧相对位置，而且通用性强。
The flip cover can easily change and accurately position the relative position of the flip cover or the flip side, and has strong universality.
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