css border shorthand

1#selector{
2    /*The format is border:width style color;*/
3    border:2px solid grey;
4}

1hr {
2  border:none;
3  border-top:1px dashed #f00;
4  color:#fff;
5  background-color:#fff;
6  height:1px;
7  width:50%;
8}

1a quick note on border-style shorthand:
2
3  border-style: none none dotted; --> this means: 
4  
5   One value: it applies the same style to all four sides.
6   Two values: applies to top and bottom, the second to the left and right.
7   Three values: applies to the top, the second to the left and right, the third to the bottom.
8   Four values: applies to all four sides following clockwise.
9