container的类描述：
.container{ padding-right:15px; padding-left:15px; margin-right:auto; margin-left:auto}@media (min-width:768px){ .container{ width:750px }}@media (min-width:992px){ .container{ width:970px }}@media (min-width:1200px){ .container{ width:1170px }}.container{ padding-right:1
