What is what, which operation in this code is responsible for what?

Question

HTML

.menu_nav {
margin:0 auto;
padding:0 30px;
height:55px;
border:1px solid #ebeadf;
}
.menu_nav ul {
list-style:none;
padding:0;
height:47px;
float:left;
border-left:1px solid #ebeae3;
}
.menu_nav ul li {
margin:0;
padding:0;
float:left;
border-right:1px solid #ebeae3;
}
.menu_nav ul li a {
display:block;
margin:0;
padding:12px 24px 13px;
color:#0A0A0A; background-color:#cbcac0;
text-decoration:none;
font-size:13px;
}
.menu_nav ul li.active a, .menu_nav ul li a:hover {
color:#fff;

Answer 1

All here htmlbook.ru/css