a#o_nas {
display:block;
height:25px;
width:113px;
background-image:url("./graph/zoo_off.png");
float:left;
}

a:hover#o_nas {
display:block;
height:25px;
width:113px;
background-image:url("./graph/zoo_on.png");
}

a#ksiega {
display:block;
height:25px;
width:139px;
background-image:url("./graph/ksiega_off.png");
float:left;
}

a:hover#ksiega {
display:block;
height:25px;
width:139px;
background-image:url("./graph/ksiega_on.png");
}