var ids = new Array("year1", "year2", "year3");

function switchid(id)
{
    hideallids();
    showdiv(id);
}

function hideallids()
{
    for (var i=0; i<ids.length; i++)
        hidediv(ids[i]);	  
}

function hidediv(id)
{
    if (document.getElementById)
        document.getElementById(id).style.display = "none";
    else
    {
        if (document.layers)
            document.id.display = "none";
        else
            document.all.id.style.display = "none";
    }
}

function showdiv(id)
{		  
    if (document.getElementById)
        document.getElementById(id).style.display = "block";
    else
    {
        if (document.layers)
            document.id.display = "block";
        else
            document.all.id.style.display = "block";
    }
}