function show_(div_id) {

    show   = 'show'    + div_id;
    hide   = 'hide'    + div_id;
    div_id = 'content' + div_id;

    // hide the show
    document.getElementById(show).style.display = 'none';

    // show the hide
    document.getElementById(hide).style.display = 'inline';

    // show the requested div
    document.getElementById(div_id).style.display = 'block';
}
function hide_(div_id) {

    show   = 'show'    + div_id;
    hide   = 'hide'    + div_id;
    div_id = 'content' + div_id;
	
    // hide the hide
    document.getElementById(hide).style.display = 'none';

    // show the show
    document.getElementById(show).style.display = 'inline';

    // hide the requested div
    document.getElementById(div_id).style.display = 'none';
}