function rollon(mainnav,captionid,display){
    mainnav.className="navhighlight";
    if(captionid)
    {
        var element = document.getElementById( captionid );
        if(!element)
        {
            alert("could not find caption"+captionid)
        }
        else
        {
            element.className="captionon"
        }
    }
    if(display)
    {
        var element = document.getElementById( display );
        if(!element)
        {
            alert("could not find caption"+display)
        }
        else
        {
            element.className="captionoff"
        }
    }
}
    
function rolloff (mainnav,captionid,display){
    mainnav.className="navbutton";
    if(captionid){
        var element = document.getElementById( captionid );
        if(!element){
            alert("could not find caption"+captionid)
        }
        else{
            element.className="captionoff"}
    }
    if(display){
        var element = document.getElementById( display );
    if(!element){
        alert("could not find caption"+display)
    }
    else{
        element.className="captionon"}
    }
    }
    
function linkto (mainnav){window.location=mainnav}