12:sass中宏、继承以及占位符的比较
margin-top: 10px; }
.box1 span {
display: inline-block;
margin-top: 20px; }
.box2 {
margin-top: 10px; }
.box2 span {
display: inline-block;
margin-top: 20px; }
.mt, .header1, .header1 span, .header2, .header2 span {
margin-top: 5px; }
.header1 span {
display: inline-block; }
.header2 span {
display: inline-block; }
.footer1, .footer1 span, .footer2, .footer2 span {
margin-top: 5px; }
.footer1 span {
display: inline-block; }
.footer2 span {
display: inline-block; }