Código no funciona en Firefox

[valc]

Hola alguien podria ayudarme, no puedo hacer que esta parte del codigo me ande en firefox....porfi si saben ayudenme!!!

// validar carrera



var turno = $("sel_turno");

var carr = $ ("sel_carreras");

var divs = $$("i");

var inputs = $$("input");

var divHora = divs[0];

var r1 = inputs[10];

var r2 = inputs[11];

var r3 = inputs[12];

var r4 = inputs[13];

var o = document.createElement("option");

for (var i=0;i<carreras.length;i++) {

var o = document.createElement("option");

carr.appendChild(o);

o.text=carreras[i][0];

o.selected=carreras[i][1];

o.id=i+"car";

o.value=i;

}


for (var i=0;i<turnos.length;i++) {

var f = document.createElement("option");

$("sel_turno").appendChild(f);

f.text=turnos[i][0];

f.selected=turnos[i][2];

f.title=turnos[i][1];

f.id=i+"tur";

f.value=i;

}

turno.disabled=true;

r1.disabled=true;

r2.disabled=true;

r3.disabled=true;

r4.disabled=true;



$("sel_carreras").onchange=function(){

turno.disabled=false;

turno.onchange=function(){

var indice = this.selectedIndex;

divHora.innerHTML=this.options[indice].title;

r1.disabled=false;

r2.disabled=false;

r3.disabled=false;

r4.disabled=false;

}

};



var labels = $$("label");

var ultLabel = labels[15];

ultLabel.innerHTML="";

var tam = materiasWeb[[0][0]].length;


r1.onclick=function(){

ultLabel.innerHTML="";

for (var e=0 ; e<=tam-1 ; e++){

ultLabel.style.display="";

var ul = (materiasWeb[0][e]);

var id = "1_"+e+1;

crear ("input","div",id);

crear2 ("t",ul);

}

};

r2.onclick=function(){

ultLabel.innerHTML="";

for (var i=0 ; i<=tam-1 ; i++){

ultLabel.style.display="";

var ul = (materiasWeb[1][i]);

var id = "2_"+i+1;

crear ("input","div",id);

crear2 ("t",ul);

}

};

r3.onclick=function(){

ultLabel.innerHTML="";

for (var i=0 ; i<=tam-1 ; i++){

ultLabel.style.display="";

var ul = (materiasWeb[2][i]);

var id = "3_"+i+1;

crear ("input","div",id);

crear2 ("t",ul);

}

};

r4.onclick=function(){

ultLabel.innerHTML="";

for (var i=0 ; i<=tam-1 ; i++){

ultLabel.style.display="";

var ul = (materiasWeb[3][i]);

var id = "4_"+i+1;

crear ("input","div",id);

crear2 ("t",ul);

}

};

function crear(ele,tex,id) {

var ultLabel1 = labels[15];

var a = document.createElement(ele);

var t = document.createElement(tex);

a.type="checkbox";

ultLabel1.appendChild(a);

a.id=id;

};

function crear2(ele,tex) {

var ultLabel2 = labels[15];

var a = document.createElement(ele);

ultLabel2.appendChild(a);

a.innerHTML=tex+"<br />";

};