JS not working in Firefox, works in IE and Chrome

Question

Was wondering if anyone could provide some insight as to why this js does not work in Firefox but works perfectly and as intended under IE and Chrome?

It changes the color of a lot of divs when hovering over some buttons at the top of the page.

Can be seen on my site: ptable.info

window.onload=function(){
var noblegasesColl = document.getElementsByClassName('noblegases');
var halogensColl = document.getElementsByClassName('halogens');
var othernonmetalsColl = document.getElementsByClassName('othernonmetals');
var transitionmetalsColl = document.getElementsByClassName('transitionmetals');
var metalloidsColl = document.getElementsByClassName('metalloids');
var posttransitionColl = document.getElementsByClassName('posttransition');
var alkalineColl = document.getElementsByClassName('alkaline');
var alkaliColl = document.getElementsByClassName('alkali');
var actinoidsColl = document.getElementsByClassName('actinoids');
var lanthanoidsColl = document.getElementsByClassName('lanthanoids');

//Noble Gases
document.getElementById('noblegasesButton').addEventListener('mouseover', function(){
    changeColor(halogensColl, '#696969');
    changeColor(othernonmetalsColl, '#696969');
    changeColor(transitionmetalsColl, '#696969');
    changeColor(metalloidsColl, '#696969');
    changeColor(posttransitionColl, '#696969');
    changeColor(alkalineColl, '#696969');
    changeColor(alkaliColl, '#696969');
    changeColor(actinoidsColl, '#696969');
    changeColor(lanthanoidsColl, '#696969');
});
document.getElementById('noblegasesButton').addEventListener('mouseout', function(){
    changeColor(halogensColl, '#00FFFF');
    changeColor(othernonmetalsColl, '#7CFC00');
    changeColor(transitionmetalsColl, '#ff78bb');
    changeColor(metalloidsColl, '#7A378B');
    changeColor(posttransitionColl, '#8FBC8F');
    changeColor(alkalineColl, '#e5e500');
    changeColor(alkaliColl, '#FF6600');
    changeColor(actinoidsColl, '#f4a460');
    changeColor(lanthanoidsColl, '#CC1100');
    changeColor(actinoidsColl, '#f4a460');
});
//Halogens
document.getElementById('halogensButton').addEventListener('mouseover', function(){
    changeColor(noblegasesColl, '#696969');
    changeColor(othernonmetalsColl, '#696969');
    changeColor(transitionmetalsColl, '#696969');
    changeColor(metalloidsColl, '#696969');
    changeColor(posttransitionColl, '#696969');
    changeColor(alkalineColl, '#696969');
    changeColor(alkaliColl, '#696969');
    changeColor(actinoidsColl, '#696969');
    changeColor(lanthanoidsColl, '#696969');
});

document.getElementById('halogensButton').addEventListener('mouseout', function(){
    changeColor(halogensColl, '#00FFFF');
    changeColor(othernonmetalsColl, '#7CFC00');
    changeColor(transitionmetalsColl, '#ff78bb');
    changeColor(metalloidsColl, '#7A378B');
    changeColor(posttransitionColl, '#8FBC8F');
    changeColor(alkalineColl, '#e5e500');
    changeColor(alkaliColl, '#FF6600');
    changeColor(noblegasesColl, '#3399CC');
    changeColor(lanthanoidsColl, '#CC1100');
    changeColor(actinoidsColl, '#f4a460');
});
//Non-metals
document.getElementById('nonmetalsButton').addEventListener('mouseover', function(){
    changeColor(halogensColl, '#696969');
    changeColor(noblegasesColl, '#696969');
    changeColor(transitionmetalsColl, '#696969');
    changeColor(metalloidsColl, '#696969');
    changeColor(posttransitionColl, '#696969');
    changeColor(alkalineColl, '#696969');
    changeColor(alkaliColl, '#696969');
    changeColor(actinoidsColl, '#696969');
    changeColor(lanthanoidsColl, '#696969');                    
});

document.getElementById('nonmetalsButton').addEventListener('mouseout', function(){
    changeColor(halogensColl, '#00FFFF');
    changeColor(othernonmetalsColl, '#7CFC00');
    changeColor(transitionmetalsColl, '#ff78bb');
    changeColor(metalloidsColl, '#7A378B');
    changeColor(posttransitionColl, '#8FBC8F');
    changeColor(alkalineColl, '#e5e500');
    changeColor(alkaliColl, '#FF6600');
    changeColor(noblegasesColl, '#3399CC');
    changeColor(lanthanoidsColl, '#CC1100');
    changeColor(actinoidsColl, '#f4a460');
});
//Transition metals
document.getElementById('transitionmetalsButton').addEventListener('mouseover', function(){
    changeColor(halogensColl, '#696969');
    changeColor(othernonmetalsColl, '#696969');
    changeColor(noblegasesColl, '#696969');
    changeColor(metalloidsColl, '#696969');
    changeColor(posttransitionColl, '#696969');
    changeColor(alkalineColl, '#696969');
    changeColor(alkaliColl, '#696969');
    changeColor(actinoidsColl, '#696969');
    changeColor(lanthanoidsColl, '#696969');        
});

document.getElementById('transitionmetalsButton').addEventListener('mouseout', function(){
    changeColor(halogensColl, '#00FFFF');
    changeColor(othernonmetalsColl, '#7CFC00');
    changeColor(transitionmetalsColl, '#ff78bb');
    changeColor(metalloidsColl, '#7A378B');
    changeColor(posttransitionColl, '#8FBC8F');
    changeColor(alkalineColl, '#e5e500');
    changeColor(alkaliColl, '#FF6600');
    changeColor(noblegasesColl, '#3399CC');
    changeColor(lanthanoidsColl, '#CC1100');
    changeColor(actinoidsColl, '#f4a460');
});
//Post-transition
document.getElementById('posttransitionButton').addEventListener('mouseover', function(){
    changeColor(halogensColl, '#696969');
    changeColor(othernonmetalsColl, '#696969');
    changeColor(transitionmetalsColl, '#696969');
    changeColor(metalloidsColl, '#696969');
    changeColor(noblegasesColl, '#696969');
    changeColor(alkalineColl, '#696969');
    changeColor(alkaliColl, '#696969');
    changeColor(actinoidsColl, '#696969');
    changeColor(lanthanoidsColl, '#696969');
});

document.getElementById('posttransitionButton').addEventListener('mouseout', function(){
    changeColor(halogensColl, '#00FFFF');
    changeColor(othernonmetalsColl, '#7CFC00');
    changeColor(transitionmetalsColl, '#ff78bb');
    changeColor(metalloidsColl, '#7A378B');
    changeColor(posttransitionColl, '#8FBC8F');
    changeColor(alkalineColl, '#e5e500');
    changeColor(alkaliColl, '#FF6600');
    changeColor(noblegasesColl, '#3399CC');
    changeColor(lanthanoidsColl, '#CC1100');
    changeColor(actinoidsColl, '#f4a460');
});
//Metalloids
document.getElementById('metalloidsButton').addEventListener('mouseover', function(){
    changeColor(halogensColl, '#696969');
    changeColor(othernonmetalsColl, '#696969');
    changeColor(transitionmetalsColl, '#696969');
    changeColor(noblegasesColl, '#696969');
    changeColor(posttransitionColl, '#696969');
    changeColor(alkalineColl, '#696969');
    changeColor(alkaliColl, '#696969');
    changeColor(actinoidsColl, '#696969');
    changeColor(lanthanoidsColl, '#696969');
});

document.getElementById('metalloidsButton').addEventListener('mouseout', function(){
    changeColor(halogensColl, '#00FFFF');
    changeColor(othernonmetalsColl, '#7CFC00');
    changeColor(transitionmetalsColl, '#ff78bb');
    changeColor(metalloidsColl, '#7A378B');
    changeColor(posttransitionColl, '#8FBC8F');
    changeColor(alkalineColl, '#e5e500');
    changeColor(alkaliColl, '#FF6600');
    changeColor(noblegasesColl, '#3399CC');
    changeColor(lanthanoidsColl, '#CC1100');
    changeColor(actinoidsColl, '#f4a460');
});
//Alkaline
document.getElementById('alkalineButton').addEventListener('mouseover', function(){
    changeColor(halogensColl, '#696969');
    changeColor(othernonmetalsColl, '#696969');
    changeColor(transitionmetalsColl, '#696969');
    changeColor(metalloidsColl, '#696969');
    changeColor(posttransitionColl, '#696969');
    changeColor(noblegasesColl, '#696969');
    changeColor(alkaliColl, '#696969');
    changeColor(actinoidsColl, '#696969');
    changeColor(lanthanoidsColl, '#696969');
});

document.getElementById('alkalineButton').addEventListener('mouseout', function(){
    changeColor(halogensColl, '#00FFFF');
    changeColor(othernonmetalsColl, '#7CFC00');
    changeColor(transitionmetalsColl, '#ff78bb');
    changeColor(metalloidsColl, '#7A378B');
    changeColor(posttransitionColl, '#8FBC8F');
    changeColor(alkalineColl, '#e5e500');
    changeColor(alkaliColl, '#FF6600');
    changeColor(noblegasesColl, '#3399CC');
    changeColor(lanthanoidsColl, '#CC1100');
    changeColor(actinoidsColl, '#f4a460');
});
//Alkali
document.getElementById('alkaliButton').addEventListener('mouseover', function(){
    changeColor(halogensColl, '#696969');
    changeColor(othernonmetalsColl, '#696969');
    changeColor(transitionmetalsColl, '#696969');
    changeColor(metalloidsColl, '#696969');
    changeColor(posttransitionColl, '#696969');
    changeColor(alkalineColl, '#696969');
    changeColor(noblegasesColl, '#696969');
    changeColor(actinoidsColl, '#696969');
    changeColor(lanthanoidsColl, '#696969');
});

document.getElementById('alkaliButton').addEventListener('mouseout', function(){
    changeColor(halogensColl, '#00FFFF');
    changeColor(othernonmetalsColl, '#7CFC00');
    changeColor(transitionmetalsColl, '#ff78bb');
    changeColor(metalloidsColl, '#7A378B');
    changeColor(posttransitionColl, '#8FBC8F');
    changeColor(alkalineColl, '#e5e500');
    changeColor(alkaliColl, '#FF6600');
    changeColor(noblegasesColl, '#3399CC');
    changeColor(lanthanoidsColl, '#CC1100');
    changeColor(actinoidsColl, '#f4a460');
});
//Lanthanoids
document.getElementById('lanthanoidsButton').addEventListener('mouseover', function(){
    changeColor(halogensColl, '#696969');
    changeColor(othernonmetalsColl, '#696969');
    changeColor(transitionmetalsColl, '#696969');
    changeColor(metalloidsColl, '#696969');
    changeColor(posttransitionColl, '#696969');
    changeColor(alkalineColl, '#696969');
    changeColor(alkaliColl, '#696969');
    changeColor(actinoidsColl, '#696969');
    changeColor(noblegasesColl, '#696969');
});

document.getElementById('lanthanoidsButton').addEventListener('mouseout', function(){
    changeColor(halogensColl, '#00FFFF');
    changeColor(othernonmetalsColl, '#7CFC00');
    changeColor(transitionmetalsColl, '#ff78bb');
    changeColor(metalloidsColl, '#7A378B');
    changeColor(posttransitionColl, '#8FBC8F');
    changeColor(alkalineColl, '#e5e500');
    changeColor(alkaliColl, '#FF6600');
    changeColor(noblegasesColl, '#3399CC');
    changeColor(lanthanoidsColl, '#CC1100');
    changeColor(actinoidsColl, '#f4a460');
});
//Actinoids
document.getElementById('actinoidsButton').addEventListener('mouseover', function(){
    changeColor(halogensColl, '#696969');
    changeColor(othernonmetalsColl, '#696969');
    changeColor(transitionmetalsColl, '#696969');
    changeColor(metalloidsColl, '#696969');
    changeColor(posttransitionColl, '#696969');
    changeColor(alkalineColl, '#696969');
    changeColor(alkaliColl, '#696969');
    changeColor(noblegasesColl, '#696969');
    changeColor(lanthanoidsColl, '#696969');
});

document.getElementById('actinoidsButton').addEventListener('mouseout', function(){
    changeColor(halogensColl, '#00FFFF');
    changeColor(othernonmetalsColl, '#7CFC00');
    changeColor(transitionmetalsColl, '#ff78bb');
    changeColor(metalloidsColl, '#7A378B');
    changeColor(posttransitionColl, '#8FBC8F');
    changeColor(alkalineColl, '#e5e500');
    changeColor(alkaliColl, '#FF6600');
    changeColor(noblegasesColl, '#3399CC');
    changeColor(lanthanoidsColl, '#CC1100');
    changeColor(actinoidsColl, '#f4a460');
});

}

function changeColor(coll, color){

    for(var i=0, len=coll.length; i<len; i++)
    {
        coll[i].style["background-color"] = color;
    }
}

Answer 1

You have to use either style.backgroundColor or style['backgroundColor'] to set the background-color. Either of these methods should work across browsers. I have tested in FireFox 23, Opera 15, Chrome 31 (Dev Build) and IE10.

You can refer here for a sample fiddle. The fiddle has three div with id as aa , bb and cc respectively.

When you do mouseover and mouseout , you will find that it affects all three div in Chrome, IE10 and Opera. But in FireFox, it affects only the first and third div because the second div uses style['background-color'] and is not recognized by FireFox.