.x-grid-checkheader {
    height: 14px;
    background-image: url('../images/unchecked.gif');
    background-position: 50% -2px;
    background-repeat: no-repeat;
    background-color: transparent;
}

.x-grid-checkheader-checked {
    background-image: url('../images/checked.gif');
}

.x-grid-checkheader-checked-red {
    background-color: rgba(255, 0, 0, 0.5);
    background-image: url('../images/checked.gif');
}

.x-grid-checkheader-editor .x-form-cb-wrap {
    text-align: center;
}