css寫箭頭

/* 向上的箭頭 */  
.dot-top {  
    font-size: 0;  
    line-height: 0;  
    border-width: 10px;  
    border-color: red;  
    border-top-width: 0;  
    border-style: dashed;  
    border-bottom-style: solid;  
    border-left-color: transparent;  
    border-right-color: transparent;  
}  
/* 向右的箭頭 */  
.dot-right {  
    font-size: 0;  
    line-height: 0;  
    border-width: 10px;  
    border-color: red;  
    border-right-width: 0;  
    border-style: dashed;  
    border-left-style: solid;  
    border-top-color: transparent;  
    border-bottom-color: transparent;  
}  
/* 向下的箭頭 */  
.dot-bottom {  
    font-size: 0;  
    line-height: 0;  
    border-width: 10px;  
    border-color: red;  
    border-bottom-width: 0;  
    border-style: dashed;  
    border-top-style: solid;  
    border-left-color: transparent;  
    border-right-color: transparent;  
}  
/* 向左的箭頭 */  
.dot-left {  
    font-size: 0;  
    line-height: 0;  
    border-width: 10px;  
    border-color: red;  
    border-left-width: 0;  
    border-style: dashed;  
    border-right-style: solid;  
    border-top-color: transparent;  
    border-bottom-color: transparent;  
}