a鼠标经过图像撑破

我把a转换为块元素 给了宽高值  但是出现问题     高人帮忙指点一下


.dh a:visited {
display:block;
color:#fff;
font-size:13px;
font-weight:bolder;
text-decoration:none;
background:url(images/dh_bg.jpg) repeat-x;
line-height:33px;
width:105px;
height:33px;
}
.dh a:hover {
display:block;
color:#fff;
font-size:13px;
font-weight:bolder;
text-decoration:none;
background:url(images/dh_overbg.jpg) no-repeat;
line-height:33px;
}
.dh a:active {
display:block;
color:#fff;
font-size:13px;
font-weight:bolder;
text-decoration:none;
background:url(images/dh_bg.jpg);
line-height:33px;
}