.custom-tweet-button a {
   background: url('../gfx/tnormal.jpg') 0 0 no-repeat;
   display: block;
   width: 61px;
   height: 22px;
}
.custom-tweet-button a:hover {
   background: url('../gfx/thover.jpg') 0 0 no-repeat;
}

.custom-tweet-button a:active {
   background: url('../gfx/thover.jpg') 0 0 no-repeat;
}