CSS3 nav-down 属性

实例

规定在使用方向键时向何处导航：

 button#b1
 {
 top:20%;left:25%;
 nav-index:1;
 nav-right:#b2;nav-left:#b4;
 nav-down:#b2;nav-up:#b4;
 }

 button#b2
 {
 top:40%;left:50%;
 nav-index:2;
 nav-right:#b3;nav-left:#b1;
 nav-down:#b3;nav-up:#b1;
 }

 button#b3
 {
 top:70%;left:25%;
 nav-index:3;
 nav-right:#b4;nav-left:#b2;
 nav-down:#b4;nav-up:#b2;
 }

 button#b4
 {
 top:40%;left:0%;
 nav-index:4;
 nav-right:#b1;nav-left:#b3;
 nav-down:#b1;nav-up:#b3;
 }