css button border

1.placeholder-box {
2  position: relative;
3  display: block;
4  width: 300px;
5  min-height: 150px;
6  margin-top: 50px;
7  padding: 30px;
8  border: 1px solid #888;
9  border-radius: 10px;
10  box-sizing: border-box;
11  box-shadow: 0 0 8px 0 rgba(0,0,0,0.25);
12}
13
14.placeholder-box p {
15  text-align: center;
16  margin: 0 0 15px;
17}
18
19.placeholder-box ul {
20  margin: 0;
21}
22
23/* Button */
24
25button {
26 display: block;
27 border: solid white;
28 border-width: 0 10px;
29 border-radius: 0;
30 background: green;
31 color: white;
32 font-size: 18px;
33 margin: -60px auto 15px;
34 padding: 15px;
35}

1border: 2px solid #000;