var ns4=(document.layers)?1:0;
imgL = new Array();
end=".gif";
dir="../buttons/";
function AddImg(name){
  imgL[name] = new Array(2);
  imgL[name][0] = new Image();
  imgL[name][0].src = dir + name + "_n" + end;
  imgL[name][1] = new Image();
  imgL[name][1].src =  dir + name + "_o" + end;
}

AddImg("startseite");
AddImg("unterricht");
AddImg("seminare");
AddImg("programm");
AddImg("termine");
AddImg("lehrbuch");
AddImg("vita");
AddImg("galerie");
AddImg("kontakt");

function butt(name, state){
    if(!ns4) document.images[name].src = imgL[name][state].src;
}