user/src/com/google/gwt/cell/client/ButtonCellBase.css

@sprite .buttonCellBase {
  gwt-image: 'buttonCellBaseBackground';
  height: auto;
  background-color: #f1f1f1;
  margin: 0;
  padding: 5px 7px;
  text-decoration: none;
  cursor: pointer;
  cursor: hand;
  font-size: small;
  border: 1px solid #bbb;
  border-bottom: 1px solid #a0a0a0;
  border-radius: 5px;
  -moz-border-radius: 5px;
}

.buttonCellBaseDefault {
  
}

.buttonCellBasePrimary {
  background: #666;
  color: white;
}

.buttonCellBaseNegative {
  background: #940000;
  color: white;
}

.buttonCellBase:active { /* Only works in webkit based browsers. */
  
}

.buttonCellBase:hover {
  border-color: #939393;
}

.buttonCellBase[disabled] {
  cursor: default;
  color: #888;
}

.buttonCellBase[disabled]:hover {
  border-color: #bbb #bbb #a0a0a0;
}

.buttonCellBasePushing {
  border: 1px inset #ccc;
}

.buttonCellBaseCollapseLeft {
  border-top-left-radius: 0px;
  border-bottom-left-radius: 0px;
  -moz-border-radius-topleft: 0px;
  -moz-border-radius-bottomleft: 0px;
}

.buttonCellBaseCollapseRight {
  border-right: none;
  border-top-right-radius: 0px;
  border-bottom-right-radius: 0px;
  -moz-border-radius-topright: 0px;
  -moz-border-radius-bottomright: 0px;
}