style

1/* valid */
2._user-name {
3}
4
5/* valid */
6.-user-name {
7}
8
9/* valid */
10.-user-name {
11}
12
13/* Not Valid */
14.1user-name {
15}
16
17/* Not Valid */
18.@user-name {
19}
20
21/* Not Valid */
22.user@name {
23}
24
25/* Valid */
26._user10name {
27}
28
29/* Valid */
30.u {
31}

1<!-- Write Path -->
2<link rel="stylesheet" href="assets/css/master.css" />

1/* Bad */
2.USERNAME {
3}
4
5/* Bad */
6.UserName {
7}
8
9/* Good */
10.user-name {
11}
12
13/* Bad */
14.userName {
15}
16
17/* Good */
18.usernameprofile {
19}

1<!-- Write Path -->
2<link rel="stylesheet" href="source/css/main.css" />

1<!-- External -->
2<link rel="stylesheet" href="css/file.css" />
3
4<!-- Internal -->
5<style>
6p {
7  color: red;
8}
9</style>
10
11<!-- Inline -->
12<p style="color: blue;">This Is Our Paragraph</p>