[Javscript] Problem w przeglądarce Internet Explorer

Kod:
window.onload = Laduj;



function Laduj()

{

    var menu = document.getElementById('menu');

    var podmenus = menu.getElementsByTagName('ul');

    var imgs;

    for(var a = 0; a<=podmenus.length-1; a+=1)

    {

        podmenus[a].style.display = "none";

    }

    var podmenusheads = menu.getElementsByClassName('menu');

    for(var b=0;b<=(podmenusheads.length-1);b+=1)

    {

        podmenusheads[b].onmouseover = Pokaz;

        podmenusheads[b].onmouseout = Ukryj;

    }

    for(var c = 0; c<=podmenus.length-1; c+=1)

    {

        var as = podmenus[c].getElementsByTagName('a');

        for(var d=0;d<=as.length-1;d+=1)

        {

            as[d].onmouseover = Najedz;

            as[d].onmouseout = Zjedz;

        }

    }

}



function Pokaz()

{

    var podmenu = document.getElementById(this.id);

    var uls = podmenu.getElementsByTagName('ul');

    uls[0].style.display = "block";

}



function Ukryj()

{

    var podmenu = document.getElementById(this.id);

    var uls = podmenu.getElementsByTagName('ul');

    uls[0].style.display = "none";

}



function Najedz()

{

    var a = this;

    var img = a.getElementsByTagName('img');

    img[0].src = "img/arrow_enter.png";

}



function Zjedz()

{

    var a = this;

    var img = a.getElementsByTagName('img');

    img[0].src = "img/arrow_leave.png";

}