function png_on(i) { if (document.images) { document[i].src = "/images/" + i + "_over.png"; } }
function png_off(i) { if (document.images) { document[i].src = "/images/" + i + ".png"; } }

function gif_on(i) { if (document.images) { document[i].src = "/images/" + i + "_over.gif"; } }
function gif_off(i) { if (document.images) { document[i].src = "/images/" + i + ".gif"; } }