HTML中的几种定位方式
ValueDescriptionstaticElements renders in order, as they appear in the document flow. This is default.absoluteThe element is positioned?relative to its first positioned (not static) ancestor elementfixedThe element is positioned relative to the browser windowrelativeThe element is positioned relative to its normal position, so "left:20" adds 20 pixels to the element's LEFT positioninheritThe value of the position property is inherited from the parent element

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http://www.barelyfitz.com/screencast/html-training/css/positioning/

http://davidwalsh.name/css-fixed-position

http://www.w3schools.com/cssref/pr_class_position.asp

http://www.hunuo.com/zhuanti/sheji/275.html