safari focus不能切换backgroundcolor

[Faithcsdn]

.button_gray{
font-weight: bold;
color: #FFFFFF;
text-decoration: none;
background-color: #B6B6B6;
display: block;
font-size: 8pt;
height: 20px;
margin-bottom: 0px;margin-right: 5px;
width: 120px;
padding: 3px;
border: 1px solid #FFFFFF;
border-left: 5px solid #6699CC;
float: left;
}
.button_gray:focus{
background-color: #6699CC;
border: 1px solid #FFFFFF;
border-left: 5px solid #B6B6B6;
}
在safai 不能做到点击更换border-left/background-color的颜色