Question

Что значит каждая строка ? * {
box-sizing: border-box;
}
html, body, div, span, h1, h2, h3, h4, h5, h6, p, a, ul, li{

margin: 0;
padding: 0;
border: 0;
font-size: 100%;
vertical-align: baseline;
}
body {
font-family: Verdana, Arial, sans-serif;
background-color: #f7f7f7;
}
#header{
background-color: #f4f4f4;
}
#header h1 {
font-size: 24px;
text-transform: uppercase;
font-weight: bold;
padding: 30px 30px 30px 10px;
clear: both;
}
#nav {
background-color: #eee;
border-top: 1px solid #ccc;
border-bottom: 1px solid #ccc;
}
#nav li {
float: left;
list-style: none;
}
#nav a {
display: block;
color: black;
padding: 10px 25px;
text-decoration: none;
border-right: 1px solid #ccc;
}
#nav li:last-child a {
border-right: none;
}
#nav a:hover {
font-weight: bold;
}
#nav:after {
content: " ";
display: table;
clear: both;
}
.wrapper{
background-color: #f7f7f7;
}
.aside h2 {
font-size: 0.95em;
margin-top: 15px;
}
.aside h3 {
font-size: 0.85em;
margin-top: 10px;
}
.aside p, .aside li {
font-size: .75em;
margin-top: 10px;
}
.aside li{
list-style-type: none;
}
#sidebar1 {
float: left;
width: 20%;
padding: 0 10px 0 20px;
}
#sidebar2 {
float: right;
width: 20%;
padding: 0 20px 0 10px;
}
#article{
background-color: #fafafa;
border-left: 1px solid #ccc;
border-right: 1px solid #ccc;
margin-left: 20%;
margin-right: 20%;
padding: 15px;
width: 60%;
}
#article:after{
clear:both;
display:table;
content:'';
}
#article h2{
font-size: 1.3em;
margin-bottom:15px;
}
#article p{
line-height: 150%;
margin-bottom: 15px;
}
#footer{
border-top: 1px solid #ccc;
font-size: .8em;
text-align: center;
padding: 10px 10px 30px 10px;
}
#nav ul, #header h1, .wrapper, #footer p {
max-width: 1200px;
margin: 0 auto;
}
.wrapper, #nav, #header, #footer{
min-width: 768px;
}