Clear floating effects on parent elements and adjacent elements

Clears the floating effect on parent elements and adjacent elements when the parent element is affected by the float of the child element, it can be passed "Overflow:hidden;" To clear the influence of adjacent elements affected by the float through the "clear:both;" To clear

Center arrangement

Set the margin:0 auto;width:960 of the Wrap layer "wrap", if the width is not set, because usually the wrapping layer is a block-level element, automatically fills the line, and no width is set to cause the center to be invalid.