Study 7 —— CSS美化背景和边框

图片透明度属性：opacity

背景图片重复属性：background-repeat
背景图片位置属性：background-position
                 background-postion:横坐标 纵坐标;
                 background-postion:left center;
                 background-postion:left top;
                 background-postion:left bottom;

背景图片区域属性：background-origin: border | padding | content
背景图片大小属性：background-size
背景图片显示属性：background-attachment:scroll | fixed   /* 规定图片是固定仍是随页面滑动(默认固定)*/

背景图片裁剪区域：background-clip: border-box | padding-box | content-box | no-clip背景复合属性：background: 背景颜色 背景图片 是否重复 图片位置 图片滚动;{background: background-color background-image background-repeat background-attachment              background-position background-size background-clip background-origin}边框复合属性边框样式：{border-style: border-top-style border-right-style border-bottom-style border-left-style}边框颜色：{border-color: border-top-color border-right-color border-bottom-color border-left-color}边框线宽：{border-width: border-top-width border-right-width border-bottom-width border-left-width}边框复合：{border: border-width border-style border-color}圆角边框属性：border-radius: none　| length两个圆角半径：border-radius: length/lengthborder-radius衍生属性:border-top-right-radiusborder-bottom-right-radiusborder-top-left-radiusborder-bottom-left-radius图片边框{border-imgage: image (number | percentage) (stretch | repeat | round);}