CSS问class为main的div的高度求指导！

Question

Document.maindiv{font-size:14px;height:12px;}.title{position:absolute;height:20px;}.test{height:20px;}.test2{visibility:hidden;}.test3{display:none;}titletesttest2test3main的高度是24px，请问这题要怎么分析，类选择器的优先级不是要比标签选择器更高吗