function changeClass(obj, newClass)
{
    obj.className = newClass;
}

function changeImage(obj, newImage)
{
    obj.src = newImage;
}


function back()
{
    location.replace=window.history.go(-1);
}

function cleanField(obj, defaultVal)
{
    if (obj.value == defaultVal) {
        obj.value = '';
    }
}