CSS background styles:
background-color: background color
background-image: Background image
background-repeat: repeat background image
repeat-y: the y-axis is repeated only
repeat-x: x-axis only repeated
no-repeat: Unique, displayed only once
background-position: the positioning of the background image
Value: two, respectively, represent the x and y directions, only if a write, the two values are equal
FIG. Sprite: each set of icons, the purpose is to reduce the http request
background: all of the above is to put all together
background：color image repeat position
Box model
composition:
margin: Margin distance between the box and the box
Together wrote properties
Four
When writing a time, all four are the same
Two, when, on the right, on the padded edge
Three when, on the lower right side of the padded
margin-top margin-right margin-bottom margin-left four alone could write
border: the border box
Together wrote properties
border-color color
border-top-color border-left-color
border-style upper and lower left and right pattern
border-width about the width of the upper and lower
The time of writing no need to distinguish order
padding: padding the filler
Above the lower right corner left
On the padded edge
Defined width and height only content section
content: content bought things
Box size = content + padding + border
Locate
One way css layout
Positioning: top, left, right, bottom element only in the case will be used to increase localization
Relative positioning: generally do not top, left, right, bottom
Absolute positioning: the element will flow out of the document; generally do not have margin
Fixed positioning: the element will flow out of the document, only the browser window can keep things under control
In general, the relative and absolute positioning are simultaneously occurring
All general drop-down box is absolutely positioned with relative positioning completion
float
Divided into two: left floating, floating right;
Will flow out of the document
float
clear:both 清除所有的浮动
清除浮动：不是清除自身的浮动，而是清除上一个浮动对自身造成的影响
overflow：hidden溢出隐藏，主要是用于清除浮动
overflow：scroll 溢出部分以滚动条显示
增加一个空的标签，清除所有的浮动，即可解决高度失效的问题