if (document.images)
{
    tms_link_on= new Image(68,63);
    tms_link_on.src="images/tms_button_hover.png";  
    tms_link_off= new Image(68,63);
    tms_link_off.src="images/tms_button.png";

    home_link_on= new Image(68,63);
    home_link_on.src="images/home_button_hover.png";  
    home_link_off= new Image(68,63);
    home_link_off.src="images/home_button.png";
}

function hover_on(imgName)
{
    if (document.images)
    {
        imgOn=eval(imgName + "_on.src");
        document[imgName].src= imgOn;
    }
}

function hover_off(imgName)
{
    if (document.images)
    {
        imgOff=eval(imgName + "_off.src");
        document[imgName].src= imgOff;
    }
}