var list = new Array('plas','adh','coat','cos');

function Show(obj) {
    for (var i = 0; i < list.length; i++)
    {
        document.getElementById(list[i] + "_off").style.display = "block";
        document.getElementById(list[i] + "_on").style.display = "none";
    }
    document.getElementById(obj + "_off").style.display = "none";
    document.getElementById(obj + "_on").style.display = "block";
}