function change_brand(x)
{
if (x == 'brands'){
location='./index.html?brand='+document.getElementById('brands').value;
}
if (x == 'series'){
location='./index.html?brand='+document.getElementById('brands').value+'&series='+document.getElementById('series').value;
}
if (x == 'model'){
location='./index.html?brand='+document.getElementById('brands').value+'&series='+document.getElementById('series').value+'&model='+document.getElementById('model').value;
}

}